Survival outcomes of patients with stage III colorectal cancer aged ≥ 80 years who underwent curative resection: the HiSCO-04 prospective cohort study.

Background: The efficacy of adjuvant chemotherapy in elderly patients aged ≥ 80 years with stage III colorectal cancer remains unclear. In parallel with a multicenter prospective phase II trial evaluating the efficacy of uracil-tegafur and leucovorin as adjuvant chemotherapy (HiSCO-03), we conducted a prospective observational study of these patients to assess survival outcomes, including those ineligible for chemotherapy.

Methods: This multi-institutional prospective cohort study included 17 institutions in Hiroshima, Japan. Patients aged ≥ 80 years with stage III colorectal cancer who underwent curative resection were enrolled. The primary endpoint was 3-year disease-free survival, and the secondary endpoints were 3-year overall and relapse-free survival. Propensity score matching was used to assess the effects of adjuvant chemotherapy on survival outcomes.

Results: A total of 214 patients were analyzed between 2013 and 2018, including 99 males and 115 females with a median age of 84 years (range 80-101 years). Recurrence occurred in 58 patients and secondary cancers were observed in 17. The 3-year disease-free, overall, and relapse-free survival rates were 63.3%, 76.9%, and 62.9%, respectively. Adjuvant chemotherapy was administered to 65 patients with a completion rate of 52%. In a study of 80 patients that adjusted for background factors using propensity score matching, patients who completed the planned treatment showed improved disease-free survival (3-year disease-free survival: completed, 80.0%; not received, 65.5%; and discontinued, 56.3%; p = 0.029).

Conclusions: Completion of adjuvant chemotherapy may improve the prognosis of patients with colorectal cancer aged ≥ 80 years, although the number of patients who would benefit from it is limited.