| disease | Colorectal Cancer |
Colorectal cancer is among the common diseases in countries such as the United States, Canada, and Western Europe, while its incidence is moderate in Eastern and Southern Europe, and low in Africa, Asia, and parts of Latin America. In fact, the colon and rectum are both part of the large intestine and are inseparable. In developed countries with high incidence rates of this disease, there has been no significant change in incidence or mortality over the past 20 years. In countries with moderate or low risk levels, colorectal cancer has shown an increasing trend. In recent years, there have been some new advances in the diagnosis, treatment, and prevention of large intestine cancer. Epidemiological and etiological studies have further clarified the relationship between diet and large intestine cancer, making it possible to prevent large intestine cancer by improving lifestyle. In pathology, a more reasonable staging system has been proposed, and in diagnosis, the importance of digital rectal examination for detecting rectal cancer has been emphasized. Fiber colonoscopy is a feasible method for early detection of the disease. Over the past few decades, advancements in various biological technologies have highlighted the importance of selecting treatment plans based on tumor biology. However, the role of surgery in treating colorectal tumors has not diminished. Surgical treatment emphasizes the en bloc resection of the tumor and regional lymph nodes, improving surgical techniques to preserve and reconstruct the anus as much as possible while increasing cure rates, thereby enhancing quality of life. Additionally, comprehensive treatments such as radiotherapy, chemotherapy, and immunotherapy have been developed. Preoperative radiotherapy can shorten the disease stage, increase surgical resection rates, and reduce distant metastasis rates, while postoperative radiotherapy can lower recurrence rates. Chemotherapy still primarily uses 5-fluorouracil-based drugs.
bubble_chart Pathological Changes(I) Gross Types The unified gross classification standard for large intestine cancer nationwide in 1982 is as follows.
1. Early-stage colorectal cancer:
refers to cases where the cancerous tissue is confined to the mucosal or submucosal layers of the colorectal wall, generally without lymph node metastasis. Early-stage cancer can be divided into four types. ① Flat type: mostly intramucosal carcinoma. ② Polypoid elevated type (Type I): can be further subdivided into pedunculated (IP) and sessile subtypes based on the morphology of the tumor stalk. Polypoid elevated types are mostly intramucosal carcinomas histologically. ③ Flat elevated type (IIa): the tumor appears as a coin-like elevation on the mucosal surface, mostly submucosal carcinoma. ④ Flat elevated with ulcer type (III): the tumor is saucer-shaped with elevated edges and a central depression, all of which are submucosal carcinomas.
2. Advanced colorectal cancer:
(1) Elevated type: the tumor protrudes into the intestinal lumen as nodular, polypoid, or cauliflower-like elevations with clear boundaries, either pedunculated or sessile. If the tumor surface undergoes necrosis, forming a shallow ulcer resembling a saucer, it is classified as a separate subtype called the saucer type. Its characteristics include: the tumor elevates into the intestinal lumen in a saucer-like shape with clear boundaries, a broad base, and a shallow ulcer on the surface, with the base generally higher than the intestinal mucosa. This type of cancer usually progresses slowly and has a better treatment outcome.
(2) Ulcerative type: the tumor forms a deep ulcer (generally reaching or exceeding the muscular layer) with elevated edges. This type has a poorer prognosis. Based on the ulcer's appearance and growth pattern, it can be further divided into two subtypes. ① Localized ulcer type: the tumor resembles a crater, with tumor tissue at the ulcer edges forming a raised rim above the mucosal surface, and the ulcer center showing necrosis, forming an irregularly shaped deep ulcer. Cross-sections reveal tumor infiltration into the deeper layers of the intestinal wall, but the boundaries remain clear. ② Infiltrative ulcer type: the tumor mainly grows by infiltrating the deeper layers of the intestinal wall, forming a central ulcer. The ulcer edges often lack a raised rim of tumor tissue and are instead covered by normal intestinal mucosa. Cross-sections show tumor infiltration into the deeper layers of the intestinal wall with unclear boundaries.
(4) Colloid type: the tumor varies in appearance, presenting as elevated, ulcerative, or diffusely infiltrative, but both the gross and cross-sectional views show a translucent, gelatinous appearance.
(II) Histological Types
1. Papillary adenocarcinoma: accounts for 7.86%. The cancerous tissue forms papillary structures of varying thickness, with a central core in the papillae. Based on growth patterns, it can be divided into two types: one where the adenocarcinoma grows toward the mucosal surface in a villous pattern, and another where the deeper glandular cavities expand into cystic structures with intraluminal papillary proliferation. Papillary adenocarcinoma has a relatively good prognosis.
2. Tubular adenocarcinoma: accounts for 67.22%. The cancerous tissue forms tubular structures and is divided into three grades based on differentiation: ① Well-differentiated adenocarcinoma: the tumor consists of glands of varying sizes, with well-differentiated columnar or tall columnar cells arranged orderly. ② Moderately differentiated adenocarcinoma: the cancer cells are poorly differentiated, varying in size, with pseudostratified nuclei and irregular arrangement, often extending to the apical cytoplasm. ③ Poorly differentiated adenocarcinoma: the tumor shows only a few irregular gland-like structures, with poorly differentiated, pleomorphic cells of varying sizes, large nuclei, scant cytoplasm, and frequent mitotic figures. Irregular cell cords and cancer nests may form.
4. Undifferentiated carcinoma: the tumor consists of diffusely arranged cancer cells in sheets or clusters without forming glandular or other organized structures.
5. Adenosquamous carcinoma: adenocarcinoma and squamous cell carcinoma coexist within the same tumor, with the two components fully mixed.
6. Small cell carcinoma: The cancer cells are small in size, slightly larger than lymphocytes. The cancer cells are often arranged in a tightly mosaic pattern with scant cytoplasm.
7. Squamous cell carcinoma: The cancer cells exhibit a typical squamous carcinoma structure, mostly grade II to poorly differentiated. Occasionally, keratinization and intercellular bridges are observed. They are predominantly located in the anal canal.
8. Carcinoid tumor: The cancer cells are relatively uniform in size, morphology, and staining. Typical carcinoid cells are polygonal, with moderate cytoplasm, round nuclei, and light staining. Various structures such as nested ribbons and acinar patterns are commonly seen.
(3) Pathological features of obstructive colorectal cancer
(1) In large intestine cancer-induced obstruction, 70% occur in the left colon, while right colon obstruction accounts for only 20–30% of large intestine cancer-induced obstructions. Among these, 30% of left colon obstructions are located at the hepatic flexure.
(2) Pathological studies indicate that 54% of obstructive cancers are infiltrative-type carcinomas, growing circumferentially with a highly significant fibrous tissue reaction. Additionally, 60% of obstructive cancers belong to Dukes' C and D stages.
bubble_chart Clinical Manifestations
(1) Changes in stool characteristics and habits
1. Hematochezia: The tumor's surface differs from normal mucosa and is prone to bleeding due to friction with stool. In lower large intestine cancer, stools tend to be dry and hard, making hematochezia common.
2. Pus-blood stool and mucus stool: Almost all anorectal tumors present with more than just bloody stools upon examination; the presence of pus cells and mucus mixed with stool is the most common manifestation.
3. Altered bowel habits: Changes in bowel habits include constipation, diarrhea, or alternating between the two, as well as incomplete evacuation and difficulty in defecation.
4. Changes in stool shape: When anorectal tumors grow to a certain size, they often alter stool shape, manifesting as thinning or deformation of stools.
(2) Abdominal pain and discomfort are common symptoms of anorectal tumors, caused by the following factors: ① Local tumor invasion; ② Intestinal irritation due to the tumor; ③ Intestinal obstruction or perforation caused by the tumor.
(3) Abdominal mass: The incidence of abdominal masses in large intestine cancer ranges from 47.7% to 80%. When the tumor is confined to the intestinal wall and not adherent to other organs or tissues, the mass may still be movable or vary with body position. When the tumor invades externally and adheres to other tissues, the mass often becomes fixed.
(4) Acute or chronic intestinal obstruction: When the tumor grows to a certain size, it can block the intestinal lumen, leading to complete or incomplete obstruction symptoms. The characteristic feature is progressive worsening, which is difficult to relieve without surgical intervention.
(5) Chronic consumptive manifestations: As the disease progresses, patients may exhibit chronic consumptive symptoms such as anemia, weight loss, and lack of strength. Advanced-stage patients may present with a cachectic state.
(6) Acute colon perforation and peritonitis manifestations: It is reported that about 6% of intestinal cancer cases are complicated by colon perforation.
(7) Clinical manifestations caused by tumor metastasis
1. Symptoms caused by local tumor infiltration: When rectal cancer extensively infiltrates the pelvis, it can cause dull pain and a sense of heaviness in the lumbar and sacral regions. When the tumor infiltrates or compresses the sciatic nerve or obturator nerve roots, sciatica and obturator neuralgia may occur. If the tumor invades the vagina and bladder mucosa, vaginal bleeding and hematuria may appear. Involvement of both ureters can lead to anuria and uremia.
2. Symptoms caused by hematogenous spread: The chance of vascular infiltration in the rectum below 6 cm from the anus is seven times higher than in the upper rectum and colon. The most common sites of hematogenous metastasis are the liver, lungs, and bones, with corresponding clinical symptoms.
3. Clinical symptoms caused by seeding dissemination: When the cancer invades the serosal surface, cancer cells can detach and enter the free abdominal cavity, seeding on the peritoneal surface, rectovesical pouch, and other areas. Rectal examination may reveal nodules in these regions.
4. Clinical symptoms of lymphatic metastasis: Supraclavicular lymph node metastasis is a manifestation of advanced-stage tumors.
Based on the above clinical manifestations, a diagnosis can be made in combination with the following examinations.
(1) Laboratory tests: Routine blood tests can determine the presence of anemia, while stool routine tests should focus on detecting red blood cells, pus cells, and intestinal cancer. The fecal occult blood test is often positive, and this simple and convenient method can serve as an initial screening tool for large intestine cancer and as a routine examination for colon diseases. For those with positive fecal occult blood test results, further examinations such as barium enema, X-ray, and endoscopy should be conducted. If the fecal occult blood test is negative but there is strong clinical suspicion of large intestine cancer, the test should be repeated or a barium enema X-ray examination should be performed.
(2) X-ray examination: X-ray examination is one of the important methods for diagnosing intestinal cancer. Barium enema examination can observe intestinal peristalsis, the morphology of the haustra, the presence of stenosis or dilation in the intestinal lumen, and any masses within the lumen. In the diagnosis of rectal cancer, double-contrast barium enema imaging helps to understand and rule out multiple primary cancers. However, it is not useful for diagnosing rectal cancer and may even create false impressions, especially for early or smaller lesions. This is because during the enema procedure, the inserted anal tube often passes through or beyond the lesion, making it invisible on X-ray, leading to a false diagnosis of no lesion.
(3) Fiber colonoscopy:
1. Indications for fiber colonoscopy:
(1) Unexplained hematochezia and persistently positive fecal occult blood, with suspicion of colon tumors.
(2) Suspected intestinal tumors or polyps detected by X-ray that require differentiation between benign and malignant.
(3) Preoperative determination of the extent of intestinal cancer lesions.
(4) Postoperative examination for recurrence of intestinal cancer.
2. Contraindications for fiber colonoscopy:
(1) Any severe acute colitis.
(2) Suspected intestinal perforation or acute peritonitis.
(3) Severe cardiopulmonary insufficiency or significant intestinal adhesions discovered after abdominal or pelvic surgery.
Fiber colonoscopy not only allows visualization of the tumor but also enables observation of its size, location, local infiltration extent, and whether the intestinal wall and surrounding tissues have adhered, thereby determining the stage and severity of the disease. Biopsy samples taken during colonoscopy for pathological examination can further confirm the nature and differentiation degree of the tumor. The excellent depth of colonoscopy is of great value for detecting small lesions that are difficult to identify with barium enema.
(4) Digital rectal examination: Approximately 80% of rectal cancers can be detected through digital rectal examination. Among cases of delayed diagnosis of rectal cancer, about 80% are due to the omission of this examination.
(5) CT diagnosis: CT is helpful in diagnosing cases where the tumor grows outward from the intestinal wall, extending to adjacent structures and blurring the outer contour of the intestinal wall.
1. CT manifestations of colon tumors include: ① Intraluminal masses, which may have smooth, sharp, or villous edges; ② Focal or circumferential thickening of the intestinal wall, with most lesions exceeding 2 cm in diameter; ③ CT values of the lesion area ranging approximately 40–60 Hu; ④ Diffuse calcification or central low-density areas due to necrosis; ⑤ Low-density mucinous adenocarcinoma lesions, with possible water-density areas; ⑥ Blurring of the intestinal wall when the tumor penetrates the serosal layer and extends outward; ⑦ Direct invasion of surrounding organs such as the stomach, pancreas, gallbladder, and rectum; ⑧ Enlargement of local and retroperitoneal lymph nodes.
2. CT manifestations of rectal cancer: ① Intraluminal solid mass of varying sizes, usually between 1-10 cm, with irregular margins that may appear lobulated. The density of the mass is related to its size; those smaller than 5 cm often have uniform density, while those larger than 5 cm may show necrosis and uneven density. ② Localized or circumferential thickening of the intestinal wall. In early-stage rectal cancer, the wall thickening is often localized but typically exceeds 6 cm. ③ Circumferential or asymmetric narrowing of the intestinal lumen with irregular morphology, varying in severity, and in severe cases, luminal occlusion. ④ Tumor infiltration into the surrounding intestinal wall. When the tumor penetrates the muscular layer to reach the serosal layer and surrounding fat layer, it manifests as blurring of the serosal surface and increased density of the perirectal fat layer. Sometimes, linear soft tissue shadows may be observed, which are generally considered direct signs of perirectal infiltration, though nonspecific and also seen in inflammatory conditions. ⑤ Invasion of adjacent tissues and organs, such as perirectal muscles, prostate, vagina, ureters, and pelvic cavity. ⑥ Signs of lymph node enlargement. ⑦ Liver metastasis. Liver metastasis is less common in rectal cancer compared to colon cancer, with metastases typically being small and multiple, while isolated metastases are rare. Some metastatic lesions may show calcification. ⑧ Cancerous perforation.
(6) Serum Carcinoembryonic Antigen (CEA) Test The CEA test lacks specific diagnostic value and has certain false positives and false negatives, making it unsuitable for screening or early diagnosis. However, it can be somewhat helpful in estimating prognosis, observing treatment efficacy, and detecting recurrence.
(7) Ultrasonography Examination Endorectal ultrasonography is a new diagnostic method aimed at assessing the extent of external invasion by rectal cancer and the degree of tumor infiltration into the rectal wall.
bubble_chart Treatment Measures
1. Surgical Treatment of Intestinal Cancer
Principles of Surgical Treatment: ① Complete removal of malignant tissue. ② Total or partial resection of the cancerous organ. ③ Elimination of the main pathways of lymphatic spread. ④ To prevent tumor cell emboli formation during intraoperative manipulation of the tumor membrane, venous blood flow should be controlled early.
2. Surgical Treatment of Rectal Cancer
Radical Principles for Rectal Cancer: The principle of radical treatment involves the removal of the rectum along with a segment of the blood vessels above it, as well as the surrounding tissues and potentially metastatic lymphatic drainage areas. Radical methods are divided into two categories: one involves complete resection of the rectum and anal canal followed by the creation of an artificial anus; the other involves partial resection of the rectum while preserving the anal sphincter. Factors influencing the choice of surgery include the following:
1. Tumor Location: If the tumor is located in the upper third of the rectum (upper or middle segment), and after adequate mobilization of the rectum, its lower edge is more than 10 cm from the anus, an anterior resection preserving the anus may be performed. For tumors in the lower third (lower rectal or anal canal cancer), where the lower edge of the lesion is less than 6 cm from the anal verge, a Miles’ operation is recommended, with either abdominal wall colostomy or perineal anal reconstruction as appropriate. For tumors in the middle third (lower edge 6–10 cm from the anal verge), the choice of surgical approach is more controversial and should be based on tumor size, degree of differentiation, and extent of local infiltration.
2. Pathological Type: For carcinoma in situ, 1 cm of the rectum below the tumor edge may be excised. For ulcerative, cauliflower-like, or annular cancers, 4–5 cm of the rectum below the tumor edge should be removed. For infiltrative cancers, more than 7 cm of the rectum below the tumor edge should be excised.
3. Gender, Body Type, and Age: Women have a wider pelvis, making dissection and anastomosis easier, so anal preservation should be prioritized. Men have a narrower pelvis, making anastomosis more difficult, so anal preservation should be approached cautiously. Tall and thin patients are more suitable for anal-preserving surgery, while short and stocky patients are less so. Young patients with rectal cancer are prone to early metastasis, and the malignancy is generally more aggressive. Miles’ operation is often preferred. For patients over 60 years old, palliative treatment may be chosen due to poor overall health.
4. Differentiation and Fixation: Poorly differentiated cancers have a high local recurrence rate, requiring wider margins and thorough lymph node dissection. Moderately to well-differentiated cancers are less aggressive, allowing for narrower margins. If the cancer is fixed to surrounding tissues or organs, they should be resected en bloc, followed by reconstruction or diversion based on the organs removed.
5. Advanced-stage rectal cancer with distant metastasis is not suitable for radical surgery. Palliative resection or proximal colostomy to relieve obstruction should be considered.
3. Radiation Therapy for Large Intestine Cancer
Although surgical resection is the primary treatment for colorectal cancer, the local recurrence rate after surgery alone is high because most patients are not in the early stages at the time of surgery. The local recurrence rate is approximately 25–30% for Dukes' B stage and around 50% for Dukes' C stage. Most local recurrences occur within the pelvis, as tumor invasion into perirectal soft tissues cannot be completely removed surgically. Therefore, pelvic radiotherapy is the only effective method to eliminate these residual cancer cell deposits. However, preoperative and postoperative radiotherapy show limited efficacy in colorectal cancer patients. Radiation therapy is only suitable for intraoperative radiotherapy in colorectal cancer patients.
(1) Radiotherapy Plans for Large Intestine Cancer
1. Radical Radiotherapy: Complete eradication of tumor cells through radiotherapy is only applicable to a few early-stage patients or those with highly radiosensitive tumor types.
2. Palliative Radiotherapy: Aimed at symptom relief, such as pain control, hemostasis, reducing secretions, shrinking tumors, or controlling tumor growth.
3. Combined Radiotherapy and Surgery: A planned combination of surgical and radiotherapeutic approaches.
(2) Modes of Radiotherapy for Large Intestine Cancer
1. Preoperative radiotherapy: Preoperative radiotherapy offers the following advantages: ① The activity of cancer cells is weakened, making it less likely for disseminated or residual cancer cells to survive during surgery. ② For large and fixed tumors that are estimated to be difficult to remove, preoperative radiotherapy can shrink the tumor, thereby improving the resection rate. ③ Radiobiological studies indicate that when blood supply or oxygen supply is reduced, cancer cells are more sensitive to radiation before surgery than after surgery.
Preoperative radiotherapy should strictly control the dose, with a moderate dose (3500～4500cGY) being appropriate, which neither increases surgical complications nor improves surgical efficacy.
2. Postoperative radiotherapy: Postoperative radiotherapy has the following advantages: ① Based on surgical findings, after the primary tumor is removed, the possible residual tumor sites are marked and localized, making the irradiation more precise, selective, and effective. ② After the primary tumor is removed, the tumor burden is significantly reduced, which helps enhance the radiation effect on residual cancer.
3. Intraoperative radiotherapy: During surgery, a single high-dose β-ray irradiation is applied to suspected residual cancer areas and areas that cannot be completely resected.
(III) Contraindications for radiotherapy in large intestine cancer
1. Severe emaciation and anemia.
2. Severe heart or kidney dysfunction that cannot be alleviated with treatment.
3. Severe infection or sepsis.
4. Local inability to tolerate further radiotherapy.
5. White blood cell count below 3×109/L, platelets below 80×109/L, or hemoglobin below 80g/L—radiotherapy is generally suspended under these conditions.
(IV) Complications of radiotherapy
1. Slightly delayed healing of perineal incisions in preoperative radiotherapy patients.
2. Symptoms such as abdominal pain, nausea, vomiting, and diarrhea.
3. Simple anal inflammation (1～2%), local perineal scarring, poor healing or sclerosis with pain (2%), and incomplete small intestine obstruction (1%).
4. Urinary incontinence (0.5～1%), small bladder syndrome, and hematuria (1.5%).
5. Pancytopenia.
(V) Adjuvant therapy for radiotherapy
1. For nausea and vomiting, administer metoclopramide or similar drugs as appropriate; for intractable vomiting, administer ondansetron.
2. For decreased white blood cell counts, administer leukocyte-boosting drugs such as vitamin B4, leucogen, or leukocyte-raising amines.
3. For skin reactions: for grade I reactions, apply talcum powder to the perineal area; for grade II reactions, apply gentian violet solution or fluocinolone acetonide ointment externally.
IV. Chemotherapy for large intestine cancer
Chemotherapy is one of the important adjuvant treatments for colorectal cancer and an indispensable component of comprehensive therapy. The goal is to prevent and reduce recurrence and metastasis, thereby improving the long-term efficacy of surgical treatment.
(I) Principles of adjuvant chemotherapy
1. Circulating occult viable tumor cells and microscopic cancer foci may exist locally, distantly, or both.
2. Treatment is most effective when the tumor burden is minimal and the cell kinetics are favorable, i.e., when the tumor burden is reduced or the growth fraction ratio is high, chemotherapy is more likely to be effective.
3. Use agents proven effective against the tumor.
4. Cytotoxic therapy shows a dose-response relationship, so the maximum tolerated dose must be given, and the treatment course must be sufficient to kill all tumor cells.
(II) Main indications for chemotherapy
1. Postoperative chemotherapy for Dukes' B and C stage patients.
2. Local chemotherapy.
3. Palliative chemotherapy for advanced-stage patients.
(III) Contraindications for chemotherapy
1. Patients in a cachectic state.
2. Patients with severe cardiovascular disease or renal dysfunction.
3. Patients with blood counts unsuitable for chemotherapy.
(IV) Methods of chemotherapy
1. Systemic intravenous chemotherapy.
2. Liver Stirred Pulse Catheter Chemotherapy: Intestinal cancer liver metastasis can cause progressive liver destruction, ultimately leading to patient death. Untreated patients with intestinal cancer liver metastasis have a median survival period of 2.5 to 6 months. Many drugs, such as 5-Fu and 5-Fu-DR (fluorouracil deoxyribonucleoside), are metabolized in the liver into low-toxicity products. Therefore, hepatic stirred pulse perfusion increases the concentration of these drugs while reducing systemic toxicity. The efficacy rate of liver stirred pulse catheter chemotherapy exceeds 50%, significantly higher than that of intravenous 5-Fu administration (approximately 20%). This is the mechanism by which chemotherapy drugs are applied via liver stirred pulse to treat liver metastatic cancer.
3. Portal vein catheterization chemotherapy: During surgery, a catheter is inserted into the mesenteric vein of the small intestine, transverse colon vein, or gastric omental vein 5 cm from the pylorus. Portal vein perfusion is typically initiated 6 hours after completing the intestinal anastomosis. A solution of 5-Fu 600 mg/m² + heparin sodium 5000 U in 5% glucose is continuously infused into the portal vein for 24 hours at a rate of 40 ml/h, lasting for 7 consecutive days.
4. Intraoperative adjuvant intracavitary chemotherapy: Intracavitary infusion of chemotherapeutic drugs is one of the measures to reduce anastomotic recurrence and an important component of aseptic techniques in colorectal tumor surgery. The method involves: During surgery, the bowel segments to be resected are first ligated with a cloth tape 8–10 cm from the tumor margin on both ends. For rectal cancer, the anus is occluded, and then 5-Fu 30 mg/kg (dissolved in 500 ml saline) is injected into the bowel lumen near the tumor. After 30 minutes, the arteries and veins supplying the resected bowel segment are ligated and divided, and the surgery is completed following standard procedures.
5. Intraperitoneal chemotherapy: Direct intraperitoneal administration increases drug concentration in the peritoneal cavity and prolongs the duration of efficacy. The drug concentration achieved via intraperitoneal administration is several hundred times higher than that of intravenous administration. Additionally, the drugs are absorbed through the portal venous system, providing better therapeutic effects on cancer cells in the portal vein and liver. Commonly used chemotherapeutic drugs include 5-Fu, MMC (mitomycin), ADM (doxorubicin), DDP (cisplatin), and MTX (methotrexate). The combination of 5-Fu and MMC has a synergistic effect, directly killing cancer cells, and is a commonly used clinical regimen. The specific method involves: Diluting the chemotherapeutic drugs in 1.5–2 L of fluid, warming to 37°C, and performing a single intraperitoneal infusion followed by clamping the catheter for 4 hours to ensure uniform drug distribution and prolonged contact with all peritoneal surfaces. The chemotherapeutic solution is then aspirated as much as possible using negative pressure to minimize drug accumulation. Typically, this is performed once daily for 5 consecutive days as one treatment cycle.
6. Stirred pulse catheter chemotherapy: For advanced-stage rectal cancer that cannot undergo radical resection or cases with early recurrence or metastasis after palliative tumor resection, stirred pulse catheter chemotherapy provides a favorable treatment option. Additionally, stirred pulse catheter chemotherapy has milder toxic reactions, reduces systemic toxicity, shortens treatment duration, and can improve surgical resection rates when applied preoperatively.
(5) Common combination chemotherapy regimens for colorectal cancer
1. FIVB 5-Fu 500 mg/m² d1–5
DTIC 150 mg/m² d1, d2
VCR 1.4 mg/m² d1, d8
BCNU 60 mg/m² d1
21 days per cycle.
2. FAM 5-Fu 600 mg/m² d1, d8, d1–5
ADM 30 mg/m² d1, d8
MMC 10 mg/m² d1
21 days per cycle.
3. CF CPT 10 mg/m² d1–10
5-Fu 500 mg/m² d1–5
21 days per cycle.
5. Treatment of liver metastases from colorectal cancer
(1) The Status and Principles of Surgical Treatment Currently, an increasing number of reports indicate that for colorectal cancer liver metastases, the application of various corresponding surgical treatments can achieve a 5-year survival rate of 20–30%. Surgical resection of colorectal cancer liver metastases has been widely recognized as an active and effective method. Generally, the following conditions may be prioritized for surgical treatment: ① When the metastatic lesion is a single nodule or involves a small range, i.e., the lesion is confined to one lobe or one side of the liver. ② Extrahepatic lesions have been ruled out, the primary lesion has been radically treated, and there are no signs of local recurrence. ③ The patient is in good overall condition, with no significant cardiac, pulmonary, hepatic, or renal dysfunction, and can tolerate the surgery. ④ Full consideration and weighing of the post-surgical survival time and the risks of the procedure. ⑤ The surgeon is required to have extensive experience in liver surgery and be capable of performing various types of complex liver operations.
(II) Modern Comprehensive Treatment For colorectal cancer with liver metastasis and sexually transmitted disease changes, in addition to surgical resection, modern comprehensive treatment should be emphasized. The recommended methods mainly include: ① When the lesion is extensive or liver resection is not suitable due to underlying liver conditions during surgery, hepatic artery ligation can be performed, which shows acceptable short-term efficacy. ② Intratumoral absolute alcohol injection can be performed under B-ultrasound guidance or through interventional radiology for regional perfusion therapy. For massive lesions, embolization therapy can be done first, followed by intermediate stage [second stage] resection when the tumor shrinks and the patient's overall condition permits.
(1) Large intestine tumor-induced intestinal obstruction
1. Pathophysiological changes
(1) Intestinal distension: The colon harbors a large number of bacteria, and the gas produced by fermentation increases significantly. Pain also leads to increased swallowing of air, impaired absorption of gastrointestinal secretions, and continuous discharge into the colon through the ileocecal valve. The proximal colon progressively distends, intra-abdominal pressure rises, the diaphragm shifts upward, and circulatory and respiratory dysfunction occur.
(2) Fluid loss: Obstruction of any cause can result in fluid loss. Particularly when strangulation occurs, significant fluid loss, severe dehydration, hemoconcentration, and reduced blood volume can lead to shock.
(3) Electrolyte imbalance: Obstruction of the large intestine involves the loss of large amounts of intestinal secretions, plasma, or blood, inevitably accompanied by electrolyte loss and acid-base imbalance, leading to severe electrolyte disturbances.
(4) Infection and toxemia: As obstruction progresses, the intestinal wall thins, permeability increases, or intestinal necrosis and perforation allow large amounts of bacteria and toxins to enter the peritoneal cavity, causing severe bacterial peritonitis and toxemia. This can result in septic shock, multiple organ failure, or even death.
2. Pathological characteristics of obstructive colorectal cancer
(1) 70% of large intestine cancer-induced obstructions occur in the left colon, while right colon obstructions account for only 20–30%. Among these, 30% of left colon obstructions are located at the hepatic flexure.
(2) Pathological studies show that 54% of obstructive cancers are infiltrative, growing circumferentially with significant fibrous tissue reaction. 60% of obstructive cancers are classified as Dukes' C or D stage.
3. Pay attention to strangulating obstruction caused by colonic obstruction. The following conditions should raise high suspicion of intestinal strangulation:
(1) Sudden onset of abdominal pain, shifting from paroxysmal to persistent, with bowel sounds transitioning from hyperactive to weakened or absent.
(2) Rapid disease progression, early onset of shock with poor response to anti-shock treatment.
(3) Obvious signs of peritoneal irritation.
(4) Asymmetric abdominal distension and fullness, with a palpable painful mass in the abdomen.
(5) Abdominal X-ray reveals isolated distended colonic loops and air-fluid levels.
(6) Dark red bloody fluid is aspirated during abdominal paracentesis.
4. Management principles for intestinal obstruction caused by large intestine cancer
(1) Stage I curative measures: Suitable for patients in relatively good condition, where the primary tumor can be radically resected without significant contraindications for primary anastomosis.
(2) Stage II non-curative measures: Emphasis should be placed on tumor resection during Stage I surgery, with Stage II surgery focusing only on restoring intestinal continuity. This applies to patients in relatively good condition with a chance for radical resection but significant contraindications for primary anastomosis.
(3) Tumor burden reduction measures: For cases where the primary lesion is resectable but not curable, efforts should be made to remove the primary lesion, with consideration for primary anastomosis or enterostomy.
(4) Symptom relief measures: For cases where tumor resection is not feasible, diversion (intestinal anastomosis) or enterostomy may be performed to alleviate intestinal obstruction symptoms.
(2) Colorectal cancer-induced perforation
1. Pathological changes and clinical manifestations
(1) Acute perforation with peritonitis: Characterized by a large tumor-induced colonic perforation communicating with the abdominal cavity, leading to acute diffuse peritonitis due to the spillage of colonic contents. Clinically, patients often exhibit varying degrees of low intestinal obstruction before perforation, with prodromal symptoms such as abdominal pain, distension, and cessation of bowel movements. Asymmetrical abdominal distension with visible intestinal loops, generalized tenderness, and muscle rigidity may be observed.
(2) Subacute perforation abscess type: Pathologically, perforation often occurs at the site of the primary cancer, and there is no colonic obstruction. Due to the continuous growth of the tumor, the central part of the cancer experiences nutritional disorders, leading to necrosis, ulceration, detachment, and communication with the abdominal cavity. Because the perforation is small and there is no obstruction in the proximal intestinal lumen, the pressure within the intestinal lumen is not high. The amount of colonic contents entering the abdominal cavity is minimal and slow, allowing surrounding tissues to form a localized encapsulated abscess or inflammatory mass. Clinically, patients often show no acute abdominal symptoms in the pre-perforation stage. By the time an abdominal abscess forms, patients may experience localized abdominal pain, persistent high fever, elevated blood cell counts, and a palpable mass with significant tenderness on abdominal examination.
(3) Chronic perforation with internal colonic fistula: The infiltrative growth of intestinal cancer involves surrounding tissues and adjacent organs, leading to adhesion with the primary carcinoma. Necrosis and detachment of the primary tumor occur. When perforation happens, it penetrates the adjacent affected organs, forming various types of colonic fistulas. Clinically common internal fistulas include colo-ileal fistula, colo-jejunal fistula, colo-duodenal fistula, and colo-gastric fistula.
2. Treatment
(1) Management of acute perforation with peritonitis: For peritonitis caused by cancerous colonic perforation, if the perforation time is short (within 3–4 hours), Neijing after brief preoperative preparation, resection of the tumor and perforation site should be attempted. If the patient is critically ill, has severe abdominal contamination, or presents with shock post-perforation and cannot tolerate major surgery, a staged approach is preferable: first-stage stoma creation and abdominal drainage, followed by second-stage tumor resection and anastomosis.
(2) Management of abscess formation due to intestinal cancer perforation: For abscesses caused by perforation in the right colon or proximal transverse colon, one-stage tumor resection and anastomosis is feasible. For abscesses caused by perforation in the distal transverse colon or left colon, Hartman's procedure is the preferred choice. If systemic toxic symptoms are severe, initial abscess drainage followed by second-stage tumor resection and anastomosis is advisable.
(3) Management of internal fistulas due to intestinal cancer: Since this type of cancerous perforation lacks an acute clinical course, emergency surgery is generally unnecessary. Elective surgery should be performed after thorough preoperative preparation, aiming for one-stage radical resection or tumor removal.
(III) Anorectal tumor bleeding is one of the main causes of lower gastrointestinal bleeding. Based on bleeding speed and clinical presentation, it can be classified into three types: acute massive bleeding, overt bleeding, and occult bleeding. The treatment principles for lower gastrointestinal bleeding caused by anorectal tumors include two aspects: first, controlling the bleeding, and second, treating the underlying tumor. The approach should be determined comprehensively based on the type of blood loss, the patient’s general condition, and tumor-related factors, either addressing one aspect alone or both simultaneously.
bubble_chart Metastasis and Spread
Intestinal cancer locally invades and spreads directly into surrounding tissues and organs. Distant spread can occur through the lymphatic system and bloodstream, with lymphatic dissemination often following the mesenteric vessels to the retroperitoneal and para-aortic lymph nodes. Anal cancer most commonly metastasizes to the inguinal lymph nodes rather than the retroperitoneal lymph nodes. Hematogenous metastasis primarily affects the liver, followed by the lungs and bones. Intestinal cancer below the peritoneal reflection tends to invade pelvic tissues bilaterally and then directly spreads to the lungs. When large intestine cancer infiltrates the serosal layer of the intestinal wall, cancer cells shed into the peritoneal cavity, leading to seeding and dissemination. Widespread seeding may result in cancerous ascites.
