Comorbidity, chemotherapy toxicity, and outcomes among older women receiving adjuvant chemotherapy for breast cancer on a clinical trial: CALGB 49907 and CALGB 361004 (alliance)

Purpose: We evaluated associations among comorbidity, toxicity, time to relapse (TTR), and overall survival (OS) in older women with early-stage breast cancer receiving adjuvant chemotherapy. Methods: Cancer and Leukemia Group B 49907 (Alliance) randomly assigned women ≥ 65 years old with stages I-III breast cancer to standard adjuvant chemotherapy or capecitabine. We reviewed data from 329 women who participated in the quality of life companion study CALGB 70103 and completed the Physical Health Subscale of the Older American Resources and Services Questionnaire. This questionnaire captures data on 14 comorbid conditions and the degree to which each interferes with daily activities. A comorbidity burden score was computed by multiplying the total number of conditions by each condition's level of interference with function. Outcomes were grade 3 to 5 toxicity, TTR, and OS. Logistic regression was used to evaluate associations between comorbidity and toxicity, and Cox proportional hazards models for TTR and survival. Results: Number of comorbidities ranged from 0 to 10 (median 2); the comorbidity burden score ranged from 0 to 25 (median 3). The most common conditions were arthritis (58%) and hypertension (55%). Comorbidity was associated with shorter OS, but not with toxicity or TTR. The hazard of death increased by 18% for each comorbidity (hazard ratio [HR] = 1.18, 95% CI = 1.06 to 1.33) after adjusting for age, tumor size, treatment, node and receptor status. Comorbidity burden score was similarly associated with OS (HR = 1.08; 95% CI, 1.03 to 1.14). Conclusions: Among older women enrolled onto a clinical trial, comorbidity was associated with shorter OS, but not toxicity or relapse.