Net survival in colon and rectal cancer by stage according to neoadjuvant treatment. A French population-based study.

Aim: Real-life estimations of survival by stage in colorectal cancer are scanty. We estimated population-based net survival by pathological stage and location, and for rectal cancer by patterns of evolution according to clinical and pathological stage with regard to neoadjuvant therapy.

Method: Age-standardized net survival was estimated on 19,630 colorectal cancers diagnosed between 2009 and 2015.

Results: Five-year net survival was 64 % for colon and 62 % for rectal cancer. The highest absolute difference between colon and rectum was 12 % for stage II women aged 75 (91% vs. 79 %). Among patients with clinical stage III rectal cancer, 67 % no longer had pathological node involvement after neoadjuvant treatment. Survival was similar in clinical stage I, II or III and pathological stage III after neoadjuvant treatment and in pathological stage III without neoadjuvant treatment (between 67 % and 72 %). It ranged between 80 and 82 % in pathological stage II, without neoadjuvant treatment or with clinical stage I, II or III before neoadjuvant treatment. Survival ranged between 93 % and 95 % in pathological stage I, treated with surgery only or with clinical stage II or III before neoadjuvant treatment.

Conclusion: Prognosis is associated with stage determined on surgical specimens rather than stage at the initial workup.