There are probably three reasons for the recurrence of cancer after surgery. First, there are a large number of residual cancer cells and incomplete treatment. Second, the patient's immunity is low after trauma such as surgery, radiotherapy, and chemotherapy. This is a good thing for the cancer cells to come back. Patients have susceptibility to certain cancers, including genetic factors and external stimulation.

There are many things to do to avoid cancer recurrence after surgery, but standardized treatment is the most important measure! So, how to treat colon cancer after surgery?

The postoperative treatment plan for colon cancer is mainly formulated based on TNM staging, which is somewhat different from the treatment plan for mid- and low-lying rectal cancer that is less than 12 cm from the anal opening.

After standardized surgical resection of stage I colon and rectal cancer, the 5-year survival rate can reach more than 90%, and no adjuvant treatment is required after surgery. If chemotherapy is given in an "intensive" or "consolidating" manner, it will generally not be beneficial to survival time but will increase unnecessary damage.

Postoperative adjuvant treatment for stage II and III colon and rectal cancer is generally "platinum agent" and "fluorouracil" alone or combined with chemotherapy. It is not recommended to use a certain "Tecan", a certain "Gio", targeted drugs, Anti-angiogenic drugs, immune preparations, etc. These drugs are mostly used for metastatic colorectal cancer or recurrence of colorectal cancer.

Whether adjuvant chemotherapy is needed after stage II colon cancer surgery is a bit more complicated. First, microsatellite instability needs to be detected. If the expression is high, chemotherapy will not be needed after surgery. If the expression is low, it still needs to be checked to see if there are any high-risk factors for recurrence. If the tumor has high-risk factors for recurrence, chemotherapy will be required after surgery. If the risk of recurrence is low, observation and chemotherapy can be performed. So, what are the high-risk factors for recurrence?

Poorly differentiated or undifferentiated adenocarcinoma with low expression of microsatellite instability.The primary tumor penetrates the intestinal wall and serosa layer, which is T4.Invasion of blood vessels and lymphatic vessels, or invasion of nerves.There was intestinal obstruction or intestinal perforation before surgery.The number of lymph nodes detected in postoperative pathological specimens was less than 12, and the staging could not be comprehensively and accurately assessed.The intestinal resection margin is positive or cannot be determined.

Stage IV colon cancer is also metastatic colon cancer. Regardless of preoperative conversion therapy or postoperative adjuvant therapy, as well as tumor recurrence, the treatment drugs will be "richer".

①Chemotherapy is based on three types of drugs: "platinum agent", "fluorouracil" and "tecan", which are combined into different treatment plans. ②Does KRAS, NRAS, and BRAF V600E need to be tested for mutations before targeted therapy? Effective if used in wild type. ③ "Bevac" anti-angiogenic drugs need to be used in combination with chemotherapy. ④ If microsatellite instability is highly expressed, immunotherapy may be considered.​