Dosage of adjuvant G-CSF (filgrastim)-supported FEC polychemotherapy based on equivalent haematological toxicity in high-risk breast cancer patients. Scandinavian Breast Group, Study SBG 9401.

Background: Conventional dosages of cytostatics in mg/m2 will cause marked variations in systemic exposure, resulting in over- and under-treatment, at least with respect to side effects.

Patients And Methods: We are conducting a randomized adjuvant study for breast cancer patients younger than 60 years of age with > or = 70% risk of recurrence within five years. The first 89 consecutive patients who have received nine courses q three weeks of individually dose-escalated and G-CSF (filgrastim)-supported FEC (5-fluorouracil (5-FU), epirubicin, and cyclophosphamide) therapy given with ciprofloxacin prophylaxis were included in this analysis. Six different FEC dose levels were used for treatment at equivalent haematological toxicity. Dose modifications were based on white blood cell and platelet counts on days 8, 11/12, 15, and 22.

Results: Eighty-three of 89 patients completed all nine courses. The median epirubicin and cyclophosphamide doses were 782 mg/m2 (range 0-994 mg/m2) and 10.330 mg/m2 (range 0-14.460 mg/m2), respectively. Patients treated at the two highest dose levels experienced NCl grade 0 or 1 toxicities in 73% to 92% of the courses. Three patients have developed acute myeloid leukaemia, and two of them have demonstrated abnormalities compatible with topoisomerase II-poison-related karyotypic changes.

Conclusions: Tailored adjuvant G-CSF-supported FEC polychemotherapy will make it possible for all patients to be treated at equivalent levels of haematological toxicity with significantly higher doses without a marked increase in other organ toxicities.