Association of multidimensional comorbidities with survival, toxicity, and unplanned hospitalizations in older adults with metastatic colorectal cancer treated with chemotherapy.

Background: Studies of older patients with colorectal cancer(CRC) have found inconsistent results about the correlation of various comorbidities with overall survival(OS) and treatment tolerance. To refine our understanding, we evaluated this correlation using the Cumulative Illness Rating Scale-Geriatric(CIRS-G) and heat maps to identify subgroups with the highest impact.

Methods: We retrospectively reviewed 153 patients aged 65 years and older with stage IV CRC undergoing chemotherapy. We calculated CIRS-G scores, and a Total Risk Score(TRS) derived from a previous heat map study. The association between CIRS-G scores/TRS and OS, unplanned hospitalizations, and chemotoxicity was examined by the Cox proportional hazards model.

Results: Median age was 71 years. Median MAX2 score of chemotherapies was 0.134(0.025-0.231). The most common comorbidities were vascular(79.8%), eye/ear/nose/throat(68%), and respiratory disease(52.4%). Median OS was 25.1 months(95% confidence interval: 21.2-27.6). In univariate analysis, ECOG PS ≥ 2(HR 1.86(1.1-3.17), p = 0.019), poorly differentiated histology(HR 2.03(1.27-3.25), p = 0.003), primary site(rectum vs colon)(HR 0.58 (0.34-0.98), p = 0.04), age at diagnosis(HR per 5y 1.20 (1.04-1.39), p = 0.012), and number of CIRS-G grade 4 comorbidities(HR 1.86 (1.1-3.17), p = 0.019) were associated with OS. In multivariate analysis, the number of CIRS-G grade 4 comorbidities lost significance, although it retained it in the subgroup of patients with colon cancer. Conversely, the TRS was associated with OS in patients with rectal cancer. No association of comorbidity with unplanned hospitalization or chemotoxicity was observed.

Conclusions: In older adults with metastatic CRC, the number of CIRS-G grade 4 comorbidities was associated with worse OS but no specific CIRS-G category was independently associated with OS, unplanned hospitalization, or toxicities.