Use of pegfilgrastim support on day 9 to maintain relative dose intensity of chemotherapy in breast cancer patients receiving a day 1 and 8 CMF regimen

Aim In several commonly used regimens, chemotherapy doses are split across different days of the cycle. We aimed to determine the feasibility of growth factor support with once-per-cycle pegfilgrastim in this setting. Methods This phase II study in breast cancer patients assessed the utility of a single 6 mg subcutaneous dose of pegfilgrastim administered on day 9 of an intravenous (IV) “split” CMF (cyclophosphamide 600 mg/m 2 , methotrexate 40 mg/m 2 and 5-fluorouracil 600 mg/m 2 ) chemotherapy regimen administered on days 1 and 8 and repeated every 28 days for 6 cycles. Results Fifty-eight patients were enrolled, with 49 completing the study. For the primary endpoint, 48 patients (83%) received ≥85% of the relative dose intensity (RDI) of chemotherapy over all 6 cycles (95% confidence interval [CI], 71–91%). Across all chemotherapy cycles, 41 patients (71%) received all scheduled cycles on time and most patients ( n =49, 84%) received ≥85% of the planned dose of all chemotherapy agents in all cycles. In total, 295/319 cycles (92%) were delivered on schedule and ≥85% of the planned dose of all chemotherapy agents were administered in 309/319 cycles (97%). Febrile neutropenia was reported in only 2 patients (3%). There were no grade 4 adverse events related to pegfilgrastim. Discussion Day 9 pegfilgrastim administration was well tolerated and provided effective protection against neutropenia in patients receiving IV CMF on days 1 and 8, allowing chemotherapy to be delivered on time and at the scheduled dose in most patients.