Risk of cancer death by comorbidity severity and use of adjuvant chemotherapy among women with locoregional breast cancer.

To examine the associations of comorbidity and chemotherapy with breast cancer- and non-breast cancer-related death.Included were women with invasive locoregional breast cancer diagnosed in 2004 from seven population-based cancer registries. Data were abstracted from medical records and verified with treating physicians when there were inconsistencies and missing information on cancer treatment. Comorbidity severity was quantified using the Adult Comorbidity Evaluation 27. Treatment guideline concordance was determined by comparing treatment received with the National Comprehensive Cancer Network guidelines. Kaplan-Meier method and multivariable Cox proportional hazards regressions were employed for statistical analyses.Of 5852 patients, 76% were under 70years old and 69% received guideline concordant adjuvant chemotherapy. Comorbidity was more prevalent in women age 70 and older (79% vs. 51%; p<0.001). After adjusting for tumor characteristics and treatment, severe comorbidity burden was associated with significantly higher cancer-related mortality in older patients (Hazard Ratio [HR]=2.38, 95% CI 1.08-5.24), but not in younger patients (HR=1.78, 95% CI 0.87-3.64). Among patients receiving guideline adjuvant chemotherapy, cancer-related mortality was significantly higher in older patients (HR=2.35, 95% CI 1.52-3.62), and those with severe comorbidity (HR=3.79, 95% CI 1.72-8.33).Findings suggest that, compared to women with no comorbidity, patients with breast cancer age 70 and older with severe comorbidity are at increased risk of dying from breast cancer, even after adjustment for adjuvant chemotherapy and other tumor and treatment differences. This information adds to risk-benefit discussions and emphasizes the need for further study of the role for adjuvant chemotherapy in these patient groups.