Comorbidities and Their Management: Potential Impact on Breast Cancer Outcomes.

Pre-existing comorbidities negatively impacts overall breast cancer prognosis, increasing both breast cancer specific deaths as well as death from competing causes. Improvements in breast cancer survival in recent decades, however, have primarily been experienced among cancer patients without comorbidities, and less so among those with moderate or severe comorbidities. As guidelines for the treatment of breast cancer are mostly based on studies excluding patients with moderate and severe comorbidities with under-representation of older women with comorbid conditions, information regarding treatment effectiveness in breast cancer patients with comorbidities is currently lacking. This chapter describes the impact of comorbidities on breast cancer treatment and outcomes, previous research approaches taken, and specific populations that may be most susceptible to the effects of comorbidities on breast cancer outcomes. Future research directions are suggested that may help to improve understanding of comorbidity-related factors that underlie disparities in breast cancer outcomes, and to examine the potential role of effective management of comorbidities among breast cancer patients as a strategy to help close gaps in disease prognosis.