Background: Cyclophosphamide-methotrexate-5-fluorouracil (CMF) is often selected as adjuvant chemotherapy for older patients with early-stage breast cancer due to perceived superior tolerability. We sought to measure persistence with CMF, adherence to oral cyclophosphamide, and the association of these with toxic effects.
Patients and methods: CALGB 49907 was a randomized trial comparing standard chemotherapy (CMF or AC, provider/patient choice) with capecitabine in patients aged ≥65 with stage I-IIIB breast cancer. Those randomized to standard therapy and choosing CMF were prescribed oral cyclophosphamide 100 mg/m(2) for 14 consecutive days in six 28-day cycles. Persistence was defined as being prescribed six cycles of at least one of the three CMF drugs. Adherence was the number of cyclophosphamide doses that women reported they had taken divided by the number prescribed. Persistence and adherence were based on case report forms and medication calendars.
Results: Of 317 randomized to standard chemotherapy, 133 received CMF. Median age was 73 (range 65-88). Seventy-one percent submitted at least one medication calendar; 65% persisted with CMF. Non-persistence was associated with node negativity (P = 0.019), febrile neutropenia (P = 0.002), and fatigue (P = 0.044). Average adherence was 97% during prescribed cycles.
Conclusions: Self-reported adherence to cyclophosphamide was high, but persistence was lower, which may be attributable to toxic effects.