Effect of primary prophylactic G-CSF use on systemic therapy administration for elderly breast cancer patients

Effective systemic therapy is vital for successful breast cancer treatment, but early onset toxicities like neutropenia hinder systemic therapy administration, especially in the elderly. Primary prophylactic use of granulocyte-colony stimulating factors (G-CSF) helps prevent neutropenia, and according to some clinical trials, facilitates chemotherapy completion. Nevertheless, evidence supporting the effectiveness of primary prophylactic G-CSF in the elderly is limited. Thus, the ASCO recommendations for primary prophylactic G-CSF use in the elderly are not explicit. This retrospective observational study examined the association between primary prophylactic G-CSF administration at the start of first course chemotherapy with adequate first course chemotherapy and radiation therapy administration in elderly breast cancer patients. The study analyzes newly diagnosed breast cancer patients receiving chemotherapy present in the SEERMedicare data from 1994 to 2003. To account for the nonrandom nature of the observational data, a non-parametric matching technique was used to pre-process the data before estimating the effect of primary prophylactic G-CSF on adequate chemotherapy and radiation therapy administration. Adequate chemotherapy was defined as administration of six or more cycles during the first course. Primary prophylactic G-CSF administered at the start of the first course chemotherapy was associated with a statistically significant increase in the probability of administration of six or more first course chemotherapy cycles by 29% [95% CI 7.7–50.6%] and any radiation therapy administration by 42% [95% CI 25.2–58.4%]. Primary prophylactic G-CSF use with the first course of chemotherapy is associated with improved chemotherapy completion rates and radiation therapy. These findings emphasize the clinical value of primary prophylactic G-CSF use for systemic therapy completion, and have implications for ASCO guidelines and medicare coverage policies.