Competing nomograms help in the selection of elderly patients with colon cancer for adjuvant chemotherapy

The extent to which ≥ 70 year patients with colon cancer benefit from adjuvant chemotherapy in the presence of competing risks remains controversial.

18,937 patients ≥ 70 years with high-risk stage II and stage III colon cancer were retrospectively reviewed from SEER database. Propensity score matching (PSM) was used to adjust for potential baseline confounding. The nomograms were developed based on the competing model to describe the individual probability of colon cancer-specific death (CCSD) and non-CCSD. The subpopulation treatment-effect pattern plot (STEPP) was used to estimate the treatment-effect heterogeneity.

In the high-risk stage II subgroup, compared to the non-recipients, the hazard ratios (HR) of overall mortality for recipients were 0.83 (P = 0.001). The subdistribution hazard ratio (SHR) of CCSD for receipts was 1.22 (P = 0.021). The SHR of non-CCSD was 0.63 (P < 0.001). In the stage III subgroup, compared to non-recipients, the HR of the overall mortality for the recipients was 0.62 (P < 0.001). The SHR of CCSD was 0.77 (P < 0.001). The SHR of non-CCSD was 0.58 (P < 0.001). The chemotherapy efficacy differed significantly by risk score of non-CCSD (non-CCSD-RS) (P < 0.001). Recipients with high non-CCSD-RS had a rate of CCSD comparative to that of non-recipients (SHR 0.90, P = 0.150) in the stage III subgroup.

A survival analysis based on the overall mortality did not correctly interpret the effect of chemotherapy. Adjuvant chemotherapy did not provide an additional benefit to patients with high-risk stage II or patients with stage III at high risk of non-cancer death.