Effect of Pathological Response After Neoadjuvant Chemotherapy on Long-term Outcomes in Locally Advanced Colorectal Cancer: A Japanese Multicenter Study.

[BACKGROUND/AIM] Few studies have examined how the response to neoadjuvant chemotherapy (NAC) for locally advanced colorectal cancer affects prognosis.

[PATIENTS AND METHODS] A total of 162 patients who received NAC followed by radical resection with curative intent between April 2016 and December 2024 were included. Patients were classified into two groups: good response (n=43) and poor response (n=119). Clinicopathological characteristics and prognosis were compared between the groups.

[RESULTS] The good response group had a lower rate of combined resection of adjacent organs (11.6% 25.2%, =0.046), higher clinical N status before NAC (93.0% 71.4%, =0.002), lower pathological T4 rate (2.3% 23.5%, <0.001), and less lymphovascular invasion (30.2% 68.9%, <0.001). Median follow-up duration was 41 months (range=1-66 months). Good responders tended to have better relapse-free survival (RFS; 83.7% 70.5%; =0.092). Overall survival was similar between the groups (88.6% 78.6% =0.629). In the poor response group, patients who received adjuvant chemotherapy had significantly better RFS than those who did not (67.3% 70.1%, <0.05).

[CONCLUSION] Patients with a good response to NAC tended to have a better prognosis. Adjuvant chemotherapy might improve outcomes in patients with poor response to NAC.