Gene expression profiling in response to radiation treatment in human breast cancer

Treatment-related morbidities have been linked to the large post-operative treatment volumes required for external beam partial breast irradiation (PBI). Alternative PBI techniques require equipment that is not readily available. To address these issues, we designed a phase I trial utilizing widely available technology to 1) evaluate the safety of a single radiation treatment delivered preoperatively to the small-volume, intact breast tumor and 2) identify imaging and genomic markers of radiation response. Women 55 or older with clinically node negative, ER+ and/or PR+, HER2-, T1 invasive carcinomas or low-intermediate grade in situ disease ≤2cm were enrolled (n=32). Intensity-modulated radiotherapy was used to deliver 15 Gy (n=8, patients 01-08), 18 Gy (n=8, patients 09-16), or 21Gy (n=16, patients 17-32) to the tumor with a 1.5cm margin. Lumpectomy was performed within 10 days. Paired pre- and post-radiation MRI images and patient tumor samples were analyzed.