No significant differences were observed in breast volume loss between five-fraction whole-breast and partial-breast radiation therapy in patients with breast cancer who underwent prior partial mastectomy, according to the results of a study presented in a poster during the American Society for Radiation Oncology (ASTRO) 67th Annual Meeting (Abstract 2979).
“Whether we did the whole breast or the partial breast, there was no difference in breast volume at 6 months or 18 months after treatment. This may provide added reassurance for patients considering five-fraction radiation therapy,” stated presenting and lead study author Elizabeth Obi, MD, of the Department of Radiation Oncology, Cleveland Clinic Foundation.
The study authors noted that these findings add to a growing body of literature supporting the use of five-fraction whole-breast radiation therapy as effective without increasing breast volume loss.
“Advances in radiation planning and delivery have made it possible to deliver breast radiation safely and effectively in just five fractions. This approach is not only convenient for patients but also resource-efficient for health-care systems. Given its proven efficacy and favorable tolerability, I believe five-fraction breast irradiation is poised to become the standard of care in the near future,” said study author Sheen Cherian, MD, also of the Department of Radiation Oncology, Cleveland Clinic Foundation.
Background and Study Methods
Radiation therapy for patients with breast cancer following breast-conserving surgery is increasingly moving toward hypofractionated techniques, yet concerns exist for long-term toxicities with ultrahypofractionated approaches.
This study enrolled patients with breast cancer who underwent a partial mastectomy prior to receiving either whole-breast radiation therapy of 26 Gy in five fractions or partial-breast radiation therapy of 30 Gy in five fractions (intensity or volumetric modulated). A total of 207 patients with stage 0 to II breast cancer who were treated at Cleveland Clinic between 2021 and 2022 were identified, and 72 patients met the eligibility criteria.
Mammograms were analyzed prior to surgery, at 6 months after radiation therapy, and at 18 months after radiation therapy to determine breast volume.
Patient Characteristics and Key Findings
The median overall patient age was 68 years; 86% of all patients were White and 14% were Black; 70 patients had invasive disease and 2 had ductal carcinoma in situ; 92% had estrogen receptor–positive disease, 85% had progesterone receptor–positive disease, and 11% had HER2-positive disease. Of the 72 patients, 49 received partial-breast and 23 received whole-breast radiation therapy.
The investigators used the previously published V=(1/3)πRccRmloHmlo to estimate breast volume from mammogram radius and height measurements of both craniocaudal and mediolateral oblique views.
Significant decreases in breast volume were observed in each cohort at both the 6- and 18-month post–radiation therapy mammograms. For the whole-breast radiation therapy arm, the mean presurgical breast volume was 1,288; it was 992 at 6 months and 924 at 18 months (P < .0001). In the partial-breast radiation therapy arm, the mean presurgical breast volume was 1,270; it was 1,076 at 6 months and 1,035 at 18 months (P < .0001).
No significant difference in these mean volumes was reported between the two treatment arms at each time point (P = .096). No significant change in breast volume was observed between the 6- and 18-month postradiation mammograms in either cohort (P = .091).
Univariate analysis showed that there were no significant differences between the cohorts in time between presurgical mammogram to radiotherapy (P = .092), radiation treatment to 6-month mammogram (P = .150), or 6-month mammogram to 18-month mammogram (P = .524).
"I would be interested in a similar volumetric analysis with a larger cohort of patients, as well as a dosimetric analysis between these two regimens," Dr. Obi added, noting that longer follow-up with larger cohorts are needed to further support these findings.
Disclosure: For full disclosures of the study authors, visit amportal.astro.org.
