Impact of relative dose intensity of FOLFOX adjuvant chemotherapy on risk of death among stage III colon cancer patients

Abstract

Background: Clinical trials have suggested high-risk (T4 and/or N2) and low-risk (T1-T3 and N1) stage III colon cancer patients might need different doses of FOLFOX to reserve a similar survival probability. Observational studies have investigated the effect of relative dose intensity (RDI) of FOLFOX on cancer survival for patients with stage III colon cancer, but nonetheless, the studies focused on very specific populations, and none performed stratified analysis by risk profiles. This study aims to identify the optimal RDI of FOLFOX administered for high-risk and low-risk stage III colon cancer patients. Methods: Data on 407 eligible patients, diagnosed with stage III colon cancer in 2011 who received FOLFOX, were collected by the eight population-based cancer registries for a CDC National Program of Cancer Registries (NPCR) project focused on Comparative Effectiveness Research. We employed Kaplan-Meier method, cumulative incidence function (CIF), Multivariable Cox model and Fine-Gray competing risks model to explore Optimal RDI defined as the lowest RDI administered without significant differences in either overall or cause-specific death. Results: Among the 168 high-risk patients, the optimal RDI cut-off point was 70% where there was no statistically significant difference in overall mortality (HR=1.59; 95% CI: 0.69-3.66) and cause-specific mortality (HR=1.24; 95% CI: 0.42-3.64) when RDI<70% vs. RDI≥70%, adjusting for sociodemographic and clinical covariates. When the RDI cut-off was lower than the optimal one (<55% vs. ≥55%, <60% vs. ≥60%, or <65% vs. ≥65%), the overall mortality was significantly statistically different between the two groups of each comparison. Among the 239 low-risk patients, none of the evaluated cut-offs were associated with statistically significant differences in overall and cause-specific mortalities between comparison groups. The lowest RDI we assessed was 45%, HR=0.80; 95% CI: 0.24-2.73 for the overall mortality and HR=0.53; 95% CI: 0.06-4.95 for the cause-specific mortality, when RDI<45% vs. RDI≥45%. Conclusions: To best utilize health care resources while maintaining efficacy, RDI can be maintained at a minimum of 70% for high-risk stage III colon cancer patients. For low-risk patients, we found that RDI as low as 45% did not significantly affect the risk of death.