- Wu, Anna;
- Kurian, Allison;
- Kwan, Marilyn;
- John, Esther;
- Lu, Yani;
- Gomez, Scarlett;
- Cheng, Iona;
- Shariff-Marco, Salma;
- Caan, Bette;
- Lee, Valerie;
- Sullivan-Halley, Jane;
- Tseng, Chiu-Chen;
- Bernstein, Leslie;
- Sposto, Richard;
- Keegan, Theresa;
- Vigen, Cheryl
BACKGROUND: The role of comorbidities in survival of patients with breast cancer has not been well studied, particularly in non-white populations. METHODS: We investigated the association of specific comorbidities with mortality in a multiethnic cohort of 8,952 breast cancer cases within the California Breast Cancer Survivorship Consortium (CBCSC), which pooled questionnaire and cancer registry data from five California-based studies. In total, 2,187 deaths (1,122 from breast cancer) were observed through December 31, 2010. Using multivariable Cox proportional hazards regression, we estimated HRs and 95% confidence intervals (CI) for overall and breast cancer-specific mortality associated with previous cancer, diabetes, high blood pressure (HBP), and myocardial infarction. RESULTS: Risk of breast cancer-specific mortality increased among breast cancer cases with a history of diabetes (HR, 1.48; 95% CI, 1.18-1.87) or myocardial infarction (HR, 1.94; 95% CI, 1.27-2.97). Risk patterns were similar across race/ethnicity (non-Latina white, Latina, African American, and Asian American), body size, menopausal status, and stage at diagnosis. In subgroup analyses, risk of breast cancer-specific mortality was significantly elevated among cases with diabetes who received neither radiotherapy nor chemotherapy (HR, 2.11; 95% CI, 1.32-3.36); no increased risk was observed among those who received both treatments (HR, 1.13; 95% CI, 0.70-1.84; P(interaction) = 0.03). A similar pattern was found for myocardial infarction by radiotherapy and chemotherapy (P(interaction) = 0.09). CONCLUSION: These results may inform future treatment guidelines for patients with breast cancer with a history of diabetes or myocardial infarction. IMPACT: Given the growing number of breast cancer survivors worldwide, we need to better understand how comorbidities may adversely affect treatment decisions and ultimately outcome.