. 2019 Feb;31(1):117–134. doi: 10.21147/j.issn.1000-9604.2019.01.07

6.

Postoperative chemotherapy

Pathological stage	Stratification	Class I recommendation	Class II recommendation	Class III recommendation
^a, Stage II patients: High-risk factors include T4 (stage IIB or IIC), poor histological differentiation [Grade 3/4, not including patients with high microsatellite instability (MSI-H)], lymphatic/vascular invasion, perineural invasion, preoperative bowel obstruction, or tumor perforation, positive or indeterminate resection margin, insufficient safety resection margin, and less than 12 lymph nodes examined. Low-risk factors refer to MSI-H or deficient mismatch repair (dMMR). Medium risk factors refer to the absence of both high- and low-risk factors. ^b, MMR testing should be considered for all stage II patients. See Section 2.3 Principles of pathological diagnosis for detailed information. Stage II patients with dMMR or MSI-H may have a better prognosis and will not benefit from 5-fluorouracil (5-FU) adjuvantmonochemotherapy (12). ^c, The specific regimen for adjuvant chemotherapy should consider the age, physical status, comorbid underlying diseases, etc. of the patient. There is currently no evidence suggesting that addition of oxaliplatin to 5-FU/leucovorin (LV) can benefit patients aged 70 years and above (13). ^d, Adjuvant chemotherapy should be started as soon as the patient recovers after surgery. This usually begins at 3 weeks after surgery and should not occur more than 2 months after surgery. The entire course of adjuvant chemotherapy is 6 months. Three months of CapeOx adjuvant chemotherapy can be considered for low-risk stage III patients (T1−3N1). ^e, Besides clinical trials, it is not recommended that the following drugs be used in adjuvant chemotherapy: irinotecan; S-1 (tegafur/gimeracil/oteracil), TAS-102, and all targeted agents including bevacizumab, cetuximab, panitumumab, aflibercept, and regorafenib.
Stage I	T1−2N0M0	Observation (Level 1A evidence)	—	—
Stage II^a,b,c,d,e	T3N0M0 with low risk factors	Observation (Level 1A evidence)	—	—
	T3N0M0 with medium risk factors	Fluorouracil monotherapy or observation (Level 1A evidence)	—	—
	T3 with high risk factors or T4N0M0	Combined chemotherapy (Level 1A evidence)	Fluorouracil monotherapy (only for pMMR) (Level 1B evidence)	Observation (Level 3 evidence)
Stage III^d,e	TanyN+M0	Combined chemotherapy (Level 1A evidence)	Fluorouracil monotherapy (Level 1B evidence)	—