Highly Accelerated Irradiation in 5 fractions (HAI-5): feasibility in elderly women with early or locally-advanced breast cancer

Abstract Rationale More than 50% of breast cancer cases occur in women aged 65 years or more. Adjuvant radiotherapy improves local control and overall survival, but is often omitted in older women because of concerns over treatment burden or logistical obstacles, even in poor prognostic groups. Accelerated radiotherapy might be an alternative to overcome these obstacles, at the condition of technical feasibility and acceptable toxicity in this frailer patient population. Research question In this prospective phase I-II trial, we investigated the safety and feasibility of delivering external beam radiotherapy in 5 fractions to the breast or thoracic wall, including boost and/or lymph nodes if needed. Methods Ninety-five patients aged 65 years or more, referred for adjuvant radiotherapy, were treated in 5 fractions over 12 days with a total dose of 28.5Gy/5.7Gy to the breast or thoracic wall and, if indicated, 27Gy/5.4Gy to the lymph node regions and 32.5Gy/6.5Gy-34.5Gy/6.9Gy to the tumor bed. The primary endpoint was clinically relevant dermatitis (≥ grade 2). Results Mean follow-up time was 5.6 months and mean age was 73.6 years. Clinically relevant dermatitis was observed in 11.6% of patients and only occurred in breast irradiation with boost (17.5% grade 2-3 versus 0% in the no-boost group). Although doses were high, treatment delivery with IMRT was swift, except for complex treatments including lymph nodes where single-arc VMAT was needed to reduce beam-on time. Conclusion Accelerated radiotherapy in 5 fractions was technically feasible and resulted in low acute toxicity. Clinically relevant erythema was only observed in patients receiving a boost, but still at an acceptable rate.