Single-Institution Phase 1/2 Prospective Clinical Trial of Single-Fraction, High-Gradient Adjuvant Partial-Breast Irradiation for Hormone Sensitive Stage 0-I Breast Cancer: 4-Year Follow-Up

Abstract

<h3>Purpose/Objective(s)</h3> We sought to evaluate the tolerability and effectiveness of a novel accelerated partial-breast irradiation regimen delivered in a single fraction postoperatively. <h3>Materials/Methods</h3> Fifty patients with low-risk, hormone-sensitive breast cancer were enrolled from 2015 to 2018 on a prospective phase 1/2 trial to receive single-fraction, high-gradient partial-breast irradiation (SFHGPBI) 2 to 8 weeks after lumpectomy for node-negative, invasive, or in situ breast cancer. The high gradient was achieved by prescribing 20 Gy to the surgical bed and 5 Gy to the breast tissue within 1 cm of the surgical bed simultaneously in one fraction using external beam radiotherapy. Follow-up was obtained at 2 and 8 weeks, 6, 12, 24, and 36 months, 4 and 5 years. Patients' cosmesis was assessed qualitatively by physicians and patients, and quantitatively by percent breast retraction assessment (pBRA). Quality of life was measured per European Organization for Research and Treatment of Cancer QOL Questionnaire BR-23. Breast cancer recurrence was surveilled via physical exam and routine mammography. <h3>Results</h3> Median age was 65 years (range, 52–84). Ten patients (20%) had small volume DCIS, while the remainder had stage I disease. Median follow-up was 50 months, at which time there were no treatment-related grade 3+ toxicities. Thirty-four percent of patients experienced grade 1 skin erythema or hyperpigmentation following their treatment, and only 2% had skin hyperpigmentation on last follow-up. Fibrosis was the most common late toxicity, occurring in 46% of participants—of which 87% of fibrosis toxicities were grade 1. Both patients and physicians assessed cosmesis as Good to Excellent in 98% of patients at last follow-up. The median quantitative cosmesis by percent of breast retraction assessment at last follow up was 4.9% (range, 0–22%) from 6.8% at baseline (range, 0–22%). At last follow-up, 76% of participants reported no pain in the affected breast; no swelling, 92%; no oversensitivity, 78%; and no skin problems, 92%. Four-year local regional control was 96%. There was one noninvasive in-breast recurrence in a separate quadrant, one isolated axillary recurrence, and four contralateral invasive breast cancers. Across the entire cohort, there have been 3 deaths in total, one of which was cancer-related (pancreatic cancer). <h3>Conclusion</h3> Accelerated partial breast irradiation delivered in a single fraction postoperatively using external beam techniques is overall well-tolerated with few grade 2 toxicities. SFHGPBI does not adversely affect cosmesis or QOL as reported by physicians and patients. Four-year local regional control remains excellent.