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William J. Gradishar, MD, FACP, FASCO


ASTRO 2022: Long-Term Outcomes With a Three-Fraction Partial-Breast Irradiation Strategy

By: Jenna Carter, PhD
Posted: Wednesday, November 23, 2022

Results from a phase II trial of a novel partial-breast irradiation technique were presented at the 2022 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 100). Robert. W. Mutter, MD, of the Mayo Clinic, Rochester, Minnesota, and colleagues assessed the long-term therapeutic effects of this irradiation regimen in patients with early-stage breast cancer. They hypothesized that using a condensed three-fraction treatment would reduce the total dose needed and improve therapeutic ratios. This hypothesis was based on previous evidence that breast cancer cells may be more sensitive to high-dose fractions than the surrounding normal tissues. Their primary outcome was nurse-assessed adverse (fair/poor) cosmesis, and their findings revealed that 4% of patients experienced adverse cosmesis at 3-year follow-up.

A total of 162 patients were treated with protons (n = 49), photons (n = 56), or brachytherapy (n = 57) partial-breast irradiation between 2015 and 2017. Biologically effective doses were established, and radiotherapy was administered on 3 consecutive days. The primary outcomes were adverse cosmesis, which was measured by the 4-point Harvard scale at 3-year follow up; this was then compared with adverse cosmesis before irradiation. Other endpoints included progression-free, local recurrence–free, and overall survival.

Overall findings revealed that the proportion of patients with adverse nurse-assessed cosmesis was 4.0% at 3 years and 5.6% at last follow-up (4.9 years). Also, at last follow-up, 92.7%, 95.9%, and 94.7%, of patients in the photon, proton, and brachytherapy cohorts had good or excellent cosmesis. Self-assessment surveys revealed that adverse cosmesis was 0% before irradiation and 2% at 3-year follow-up. Other findings revealed that at 5-year follow-up, local recurrence–free, progression-free, and overall survival rates were 97.9%, 95.1%, and 96.9%, respectively, suggesting favorable cosmetic outcomes and excellent tolerability.

Disclosure: For Dr. Mutter’s full disclosures, visit

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