Incidence of reduced chemotherapy relative dose intensity among women with early stage breast cancer in US clinical practice

Chemotherapy is widely used to treat early stage breast cancer (ESBC). Reductions and delays in dose administered—e.g., due to advanced age or febrile neutropenia (FN)—are generally believed to increase risk of disease progression and reduce survival. Little is known about incidence of reduced chemotherapy dose intensity among women with ESBC in the current era of US clinical practice. This study employed a retrospective cohort design and electronic medical records from >65 community oncology/hematology clinics in >35 states (2004–2010). The study population comprised adult women who received myelosuppressive chemotherapy for ESBC (stages I–IIIA). For each such woman, each unique cycle of chemotherapy within their first observed course was identified. Incidence of chemotherapy dose delays (≥7 days for any drug in ≥1 cycles), chemotherapy dose reductions (≥15% for any drug in ≥1 cycles), and low chemotherapy relative dose intensity (RDI