Colon cancer is currently a highly prevalent cancer, and its incidence is gradually increasing in both urban and rural areas. The treatment of colon cancer is a comprehensive treatment mainly based on surgery. With the development of medicine, the cure rate of colon cancer is gradually increasing, and the cure of many patients is already a reality. However, the overall treatment effect is still unsatisfactory, mainly because the disease is found late, and many patients do not receive regular treatment and miss the chance of cure because of various reasons. Chemotherapy is an important aspect of cancer treatment, and it is of great significance for mid- to late-stage colon cancer.
Pattern diagram of anatomical parts of the colon
Whether colorectal cancer patients need chemotherapy treatment or not mainly depends on the stage. Different staging results in different treatment plans.
If it is early stage, chemotherapy is not needed. According to TNM staging, early stage colon cancer should be T1N0M0,T2N0M0. T represents the depth of tumor invasion to the intestinal wall, T1 refers to tumor invasion to the mucosa or submucosa; T2 refers to tumor invasion to the intrinsic muscular layer of the intestinal wall; T3 refers to tumor penetration to the subplasma layer of the intestinal wall or invasion to the colorectal parietal tissue without peritoneal coverage; T4 is divided into T4a, tumor penetration to the visceral layer of the peritoneum and T4b tumor direct invasion or adhesion to other organs. T4 is divided into T4a, where the tumor penetrates the peritoneal layer and T4b, where the tumor directly invades or adheres to other organs or structures.
Staging pattern of colorectal cancer
Generally speaking, the mid-stage colorectal cancer is stage 2 and stage 3 colorectal cancer. adjuvant chemotherapy after surgery for stage 3 colon cancer is clear, and there is no controversy about chemotherapy for this stage. However, specific analysis is needed for stage 2 colorectal cancer.
Stage 2 intracolonic cancer mainly refers to the tumor invading the muscle layer of the intestinal wall or near the whole layer, and there is no metastasis of lymph nodes. For patients with this stage, whether to have chemotherapy after surgery and which regimen to choose mainly depends on whether there are combined high-risk factors (such as intestinal obstruction or perforation caused by preoperative tumor, tumor with vascular cancer embolus or nerve invasion, or poor differentiation type such as hypofractionated or indolent cell carcinoma), and whether the microsatellite is stable.
The most common metastatic route of colorectal cancer is the lymphatic route
Patients with T3 stage (2A) who have no combined high-risk factors and high microsatellite instability (MSI-H or dMMR) only need observation and regular review, and do not need chemotherapy.
Patients with T3 stage (stage 2A) who do not have combined high-risk factors but have stable or stable microsatellite highs and lows (MSI-L) can be treated without chemotherapy or with single-agent oral capecitabine chemotherapy.
If T3 stage is combined with these high-risk factors or T4 stage, although there are no lymph node metastases, patients are generally advised to have chemotherapy. The chemotherapy regimen can be single-agent oral chemotherapy (microsatellite stability check is needed before chemotherapy, and stable dosing is effective, if it is highly unstable, then it is not suitable for single-agent oral chemotherapy), or intravenous chemotherapy or intravenous combined with oral chemotherapy, of course, treatment guidelines suggest that one can also not have chemotherapy or participate in clinical studies.
How to develop postoperative chemotherapy regimen for stage 3 colon cancer.
Postoperative pathology of colon cancer shows metastasis in lymph nodes (even if there is only one metastasis), all of them belong to stage 3 colon cancer. Adjuvant chemotherapy is needed, and the duration of adjuvant chemotherapy is six months. There are two types of classic chemotherapy regimens: 2-week regimen (14 days for 1 cycle, 12 cycles in total, mFLOFOX regimen); 3-week regimen (CapeOX regimen, 21 days for 1 cycle, then a total of 8 cycles are needed).
However, in patients with low-risk stage 3 colon cancer (T1-3N1M0), there is no significant difference in prognosis between 3 months of adjuvant chemotherapy given postoperatively and 6 months of chemotherapy. n1 refers to the number of peri-intestinal lymph node metastases 1-3, T1-3 represents the depth of tumor invasion into the intestinal wall, T3 tumor penetrates the lamina propria to reach the subplasma layer or invades the paracolic tissue without peritoneal coverage. nccn guidelines recommend XELOX regimen for 3 months and FOLFOX regimen for 3-6 months, with a preference for 6 months.
Other than that for stage 3 colorectal cancer it is recommended to complete six months of adjuvant chemotherapy. Unless, the patient has significant chemotherapy side effects and cannot tolerate six months, the number can be reduced or changed to single agent oral chemotherapy as appropriate.
For patients with advanced colorectal cancer, surgery is generally not preferred and chemotherapy becomes the main treatment.
Common liver and lung metastasis of colorectal cancer
If the tumor cannot be removed radically, then the main treatment for such patients is drug therapy (chemotherapy + targeted drugs). For this type of patients, genetic testing is necessary to perfect RAS and BRAF gene testing. If mutant, then chemotherapy combined with bevacizumab is required; if wild type and left hemizygous, chemotherapy combined with cetuximab is recommended. The treatment will be evaluated every 2 months to see if it can be converted to surgically resectable. If the conversion is successful, then the primary lesion and metastases will be actively resected at the same time or in stages, and postoperative treatment will continue with medication or chemotherapy alone or without chemotherapy for observation. If there is still no chance of radical surgery, then continue to change the chemotherapy regimen drug therapy, combined or not combined with targeted drugs, liver and lung metastases can be considered local destruction treatment means (such as radiofrequency ablation or interventional embolization chemotherapy, etc.).