Highly Accelerated Irradiation in 5 Fractions (HAI-5): Feasibility in Elderly Women With Early or Locally Advanced Breast Cancer.

Purpose To investigate, in a prospective phase 1 to 2 trial, the safety and feasibility of delivering external beam radiation therapy in 5 fractions to the breast or thoracic wall, including boost and/or lymph nodes if needed, to women aged ≥65 years with breast cancer. Methods and Materials Ninety-five patients aged ≥65 years, referred for adjuvant radiation therapy, were treated in 5 fractions over 12 days with a total dose of 28.5 Gy/5.7 Gy to the breast or thoracic wall and, if indicated, 27 Gy/5.4 Gy to the lymph node regions and 32.5 Gy/6.5 Gy to 34.5 Gy/6.9 Gy 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 vs 0% in the no-boost group). Although doses were high, treatment delivery with intensity modulated radiation therapy was swift, except for complex treatments, including lymph nodes for which single-arc volumetric modulated arc therapy was needed to reduce beam-on time. Conclusion Accelerated radiation therapy 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. Although the follow-up is still short, the results on acute toxicity after accelerated radiation therapy were encouraging. A 5-fraction schedule is well tolerated in the elderly and may lower the threshold for radiation therapy in this population. [ABSTRACT FROM AUTHOR]