Time trends in utilization of G-CSF prophylaxis and risk of febrile neutropenia in a Medicare population receiving adjuvant chemotherapy for early-stage breast cancer

The purpose of this study is to assess temporal trends in the use of granulocyte colony-stimulating factor (G-CSF) prophylaxis and risk of febrile neutropenia (FN) among older women receiving adjuvant chemotherapy for early-stage breast cancer. Women aged ae<yen> 66 years with diagnosis of early-stage breast cancer who initiated selected adjuvant chemotherapy regimens were identified using the SEER-Medicare data from 2002 to 2012. Adjusted, calendar-year-specific proportions were estimated for use of G-CSF primary prophylaxis (PP) and secondary prophylaxis and FN risk in the first and the second/subsequent cycles during the first course of chemotherapy, using logistic regression models. calendar-year-specific mean probabilities were estimated with covariates set to modal values. Among 11,107 eligible patients (mean age 71.7 years), 74% received G-CSF in the first course of chemotherapy. Of all patients, 5819 (52%) received G-CSF PP, and among those not receiving G-CSF PP, only 5% received G-CSF secondary prophylaxis. The adjusted proportion using G-CSF PP increased from 6% in 2002 to 71% in 2012. During the same period, the adjusted risk of FN in the first cycle increased from 2% to 3%; the adjusted risk increased from 1.5% to 2.9% among those receiving G-CSF PP and from 2.3% to 3.5% among those not receiving G-CSF PP. The use of G-CSF PP increased substantially during the study period. Although channeling of higher-risk patients to treatment with G-CSF PP is expected, the adjusted risk of FN among patients treated with G-CSF PP tended to be lower than among those not receiving G-CSF PP.