J Breast Cancer.
2024 Apr;27(2):91-104. 10.4048/jbc.2024.0004.
Five-Fraction High-Conformal Ultrahypofractionated Radiotherapy for Primary Tumors in Metastatic Breast Cancer
- Affiliations
-
- 1Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Korea
- 2Department of Radiation Oncology, Inha University Hospital, Inha University School of Medicine, Incheon, Korea
- 3Division of Medical Oncology, Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea
- 4British Columbia Cancer Agency - Vancouver Centre, Vancouver, Canada
- 5British Columbia Cancer Agency - Centre for the North, Prince George, Canada
- KMID: 2555676
- DOI: http://doi.org/10.4048/jbc.2024.0004
Abstract
- Purpose
To report on the local control and toxicity of 5-fraction, high-conformal ultrafractionated radiation therapy (RT) for primary tumors in patients with metastatic breast cancer (MBC) who did not undergo planned surgical intervention.
Methods
We retrospectively reviewed 27 patients with MBC who underwent 5-fraction high-dose ultrafractionated intensity-modulated RT for their primary tumors between 2017 and 2022 at our institution. A median dose of 66.8 Gy (range, 51.8–83.6 Gy) was prescribed to the gross tumor, calculated in 2-Gy equivalents using an α/β ratio of 3.5, along with a simultaneous integrated boost of 81.5%. The primary endpoint of this study was local control.
Results
The median tumor size and volume were 5.1 cm and 112.4 cm3 , respectively. Treatment was generally well tolerated, with only 15% of the patients experiencing mild acute skin toxicity, which resolved spontaneously. The best infield response rate was 82%, with the objective response observed at a median time of 10.8 months post-RT (range, 1.4–29.2), until local progression or the last follow-up. At a median follow-up of 18.3 months, the 2-year local control rate was 77%. A higher number of prior lines of systemic therapy was significantly associated with poorer 2-year local control (one–two lines, 94% vs three or more lines, 34%; p = 0.004). Post-RT, 67% of the patients transitioned to the next line of systemic therapy, and the median duration of maintaining the same systemic therapy post-RT was 16.3 months (range, 1.9–40.3).
Conclusion
In our small dataset, 5-fraction, high-conformal ultrahypofractionated breast RT offered promising 2-year local control with minimal toxicity. Further studies are warranted to investigate the optimal dose and role in this setting.
