VIII. Clinical manifestations and treatment of non-metastatic diseases
1. Diagnosis and treatment of malignant polyps
Malignant polyps are defined as cancer invading the submucosa. Polyps that do not invade the submucosa will not show regional lymph node metastasis if they are carcinoma in situ. The need for further surgical excision after endoscopic removal of adenomatous polyps or adenomas requires evaluation of pathological findings and consultation with the patient.
Whether invasive carcinoma is found within a tipped or untipped polyp (adenoma), if the resection is complete and the histologic features are good, no further surgery is required. Good histologic features include grade 1 or 2, no vascular lymphatic invasion, and negative cut margins. Colonic resection is also feasible for completely removed, single clot-free polyps with good histologic features and negative cut margins because of the significantly higher incidence of negative outcomes in clot-free polyps, including recurrence, mortality, and hematogenous metastases.
If the specimen is fragmented, the margins cannot be evaluated, or the specimen has poor histologic features, colectomy, whole lymph node dissection, or optional laparoscopic resection is recommended. Poor histologic features include grade 3 or 4, vascular lymphatic invasion, and positive margins. Positive margins can be defined as the presence of tumor within 1-2 mm of the cross-sectional margin or tumor cells within the thermal ablation cross-section.
All patients with resected polyps should undergo full colonoscopy to exclude other polyps and endoscopic follow-up. chemotherapy is not recommended for stage I patients.
2. Diagnosis and treatment of invasive non-metastatic colon cancer
PET/CT is not a routine baseline examination, but can be considered if CT or MRI shows suspicious abnormalities and cannot be determined, especially if the findings may change the treatment strategy. strategy. PET/CT is not recommended for lesions smaller than 1 cm.
In the case of resectable colon cancer producing complete bowel obstruction, colon resection with complete removal of regional lymph nodes should be performed, followed by colon resection after diversion or stenting if required. Stenting is usually used for distal damage, and stenting can remove proximal colonic pressure to facilitate anastomosis for elective colectomy. If the colon cancer is locally unresectable or the patient cannot tolerate surgery, chemotherapy is recommended for conversion to resectable state.
(1) Surgical treatment
For resectable non-metastatic colon cancer, the preferred surgical treatment is colectomy and whole resection of regional lymph nodes. The procedure of colon resection needs to be based on the location of the tumor and the regional lymph nodes contained in the resected bowel and arterial arch. Other lymph nodes such as the lymph nodes at the beginning of the vein that feeds the tumor and suspicious lymph nodes outside the resection area should also be resected and biopsied if possible. The surgery should be performed for curative purposes as far as possible, and those positive lymph nodes not resected should be resected for R2.
(2) Laparoscopic colectomy
The committee recommends that laparoscopic colectomy is only feasible with an experienced surgeon and that total abdominal exploration is part of the procedure. It is not recommended for obstruction, perforation, or clear invasion of surrounding structures by the tumor. Laparoscopic surgery is not recommended for patients at high risk of abdominal adhesions, and should be converted to open surgery if adhesions are found intraoperatively.
3.Adjuvant chemotherapy for resectable colon cancer
(1) Adjuvant chemotherapy is of great benefit, and the choice of chemotherapy is mainly based on the stage of disease.
① Stage I patients do not need any adjuvant therapy
(2) Low-risk stage II patients can be enrolled in clinical trials, either for observation or for consideration of capecitabine or 5-FU/LV therapy. FOLFOX is not recommended for the treatment of stage II patients without high-risk factors.
Adjuvant chemotherapy with regimens including 5-FU/LV, capecitabine, FOLFOX, CapeOX or FLOX should be considered for stage II patients with high risk factors, including T4, poor differentiation (except MSI-H), lymphovascular invasion, perineural invasion, intestinal obstruction, perforation or perforation in close proximity to the tumor, uncertain or positive margins, or fewer than 12 lymph nodes. observation may also be considered.
Adjuvant chemotherapy at 6 months postoperatively is recommended for stage III patients with regimens including FOLFOX (preferred), CapeOX (preferred), FLOX, 5-FU/LV, and capecitabine for patients who are not candidates for oxaliplatin therapy. The committee does not recommend bevacizumab, cetuximab, panitumumab, and irinotecan for adjuvant treatment of nonmetastatic disease.
⑤ Stage II patients with MSI-H have a good prognosis and will not benefit from adjuvant 5-FU therapy. The committee recommends that MMR should be performed in stage II patients, and poorly differentiated pathological types are not considered high risk factors if accompanied by MSI-H.
(2) Polygenic analysis
There are several multigene analyses that hold promise for providing prognostic and predictive information to help decide whether to pursue adjuvant chemotherapy in patients with stage II or III disease. Oncotype DX examines seven genes at risk of recurrence and five reference genes to classify patients as low, intermediate, or high risk of recurrence. The trial showed that it did have significance for relapse, OS, and DFS in stage II or III patients, but did not predict whether adjuvant chemotherapy would be beneficial.
ColoPrint for 18 genetic tests classified prognosis as low and high risk, and the risk of recurrence confirmed by ColoPrint was independent of other risk factors such as T-stage, perforation, number of lymph nodes, and tumor grade. coIDx was used to detect high risk of recurrence in stage II colon cancer, and the risk of recurrence confirmed by CoIDx was independent of other risk factors.
Although the above tests can obtain more assessment of the risk of recurrence, the committee questioned their value and there is no evidence to predict the potential benefit of chemotherapy, so polygenic tests are not currently recommended to decide whether to administer adjuvant chemotherapy.
(3) Adjuvant chemotherapy in elderly patients
The use of adjuvant chemotherapy declines as patients age, and questions about the safety and efficacy of chemotherapy in older patients are difficult to answer. Population studies have shown that older patients can benefit from adjuvant therapy, and some studies have shown similar benefits and toxicity of 5-FU/LV adjuvant therapy in older and younger patients. The committee cautioned that the therapeutic benefit of adding oxaliplatin to 5-FU/LV in stage II and III patients over 70 years of age has not been demonstrated.
(4) Timing of adjuvant therapy
One study showed a 14% reduction in OS for every four-week delay in chemotherapy, so adjuvant chemotherapy should be started as early as the patient can afford.
(5) Adjuvant radiotherapy
Radiation therapy administered in conjunction with 5-FU-containing chemotherapy should only be used for highly selected patients, such as T4 tumors penetrating to fixed structures or recurrence. The radiotherapy area includes the tumor bed. Intraoperative radiotherapy is suitable for patients who need incremental radiotherapy, and if intraoperative radiotherapy is not possible, external irradiation in increments of 10-20 Gy or brachytherapy can be used. Preoperative combined 5-FU radiotherapy helps resectability and confocal radiotherapy should be used. Intensity modulated radiotherapy can reduce toxicity to normal tissues and should be applied in special cases such as re-radiotherapy for recurrent patients.