A Retrospective Analysis of Metronomic Cyclophosphamide, Methotrexate, and Fluorouracil (CMF) Versus Docetaxel and Cyclophosphamide (TC) as Adjuvant Treatment in Early Stage, Hormone Receptor Positive, HER2 Negative Breast Cancer

We evaluated the efficacy and tolerability of cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) vs. docetaxel and cyclophosphamide (TC) in the adjuvant treatment of 98 early-stage breast cancer patients. At an average follow-up of 35.9 and 28.2 months for CMF and TC, respectively, there was no difference in overall or disease-free survival. On average dose intensity >= 85% was maintained regardless of regimen. There was a trend towards increased Grade 3 and 4 toxicities and hospitalizations with TC vs. CMF. Background: Anthracycline and taxane-based doublets have largely replaced cyclophosphamide, methotrexate, and fluorouracil (CMF) as preferred regimens in the adjuvant treatment of breast cancer. Metronomic CMF is associated with improved tolerability over anthracycline or taxane-based regimens. Previously, there have been no direct comparisons between taxane-based regimens and CMF. Materials and Methods: We performed a retrospective review of 98 breast cancer patients treated at the Seattle Cancer Care Alliance from February 2015 through December 2018 that received either metronomic CMF or docetaxel and cyclophosphamide (TC) as adjuvant therapy for early-stage, hormone receptor-positive/human epidermal growth factor receptor-2 negative (HR+/HER2-) breast cancer. The primary outcome assessed was disease-free survival (DFS). Secondary outcomes included overall survival (OS), dose intensity, and adverse effects. Results: With an average follow-up of 35.9 and 28.2 months for CMF and TC, respectively, there was no significant difference in DFS or OS between the chemotherapy regimens. DFS at 3 years was 96.7% vs. 94.3% and OS 96.7% vs. 100% for CMF and TC, respectively. There were more dose delays in the CMF group, but on average, patients receiving either regimen achieved a dose intensity >= 85%. There was a trend towards increased hospitalization or emergency department utilization (23.1% vs. 10.6%) and Grade 4 toxicities (9.6% vs. 4.3%) with TC vs. CMF. Conclusion: Metronomic CMF offers equivalent survival outcomes to TC and remains a viable option in the adjuvant treatment of HR+/HER2- breast cancer. There was a trend towards increased Grade 4 toxicities and hospitalizations with TC, suggesting that metronomic CMF may offer a more tolerable treatment option while maintaining excellent disease outcomes.