Original Article
CyberKnife stereotactic body radiotherapy and CyberKnife accelerated partial breast irradiation for the treatment of early breast cancer
Abstract
Introduction: Stereotactic body radiotherapy (SBRT) and accelerated partial breast irradiation (APBI) delivered using the CyberKnife radiosurgery system allows coverage of the lumpectomy cavity comparable to brachytherapy without being invasive. Here we review our combined experience treating 46 stage I postlumpectomy patients with this approach.
Methods: Twenty-one patients at the Swedish Medical Center in Seattle were treated with total doses ranging from 25-36 Gy delivered in 5 to 10 equal fractions. Twenty-six patients at Winthrop University Hospital were treated with 30 Gy in 5 equal fractions. Margin and isodose schemes differed between sites, but were chosen to assure lumpectomy cavity coverage, including a margin to account for potential microscopic disease and a small margin to account for residual uncertainty, and low doses to organs at risk. Patient setup methods varied between sites but were devised to assure reproducibility and optimal beam delivery angles. Radiation was delivered while tracking and correcting for respiratory motion with the Synchrony respiratory motion management system.
Results: Mean follow-up was 31 months (range, 6-57 months) at Swedish and median follow-up was 22 months (range, 7-39 months) at Winthrop. Local control was obtained and continues in all patients. One patient reported minor pain at the lumpectomy site 10 months post-treatment, a second had palpable, non-painful firmness at the lumpectomy site, and a single patient showed Grade 1 dry skin desquamation. No serious toxicity has been observed. The cosmesis was good-excellent in all 46 patients using the Harvard cosmesis scale.
Conclusions: CyberKnife SBRT/APBI appears safe with low toxicity and excellent short-term local control. Centers interested in CyberKnife SBRT/APBI for their patients should consider treating on protocol in Investigational Review Board-approved studies, or at least according to the American Society for Radiation Oncology (ASTRO) eligibility guidelines for women with early-stage breast cancer.
Methods: Twenty-one patients at the Swedish Medical Center in Seattle were treated with total doses ranging from 25-36 Gy delivered in 5 to 10 equal fractions. Twenty-six patients at Winthrop University Hospital were treated with 30 Gy in 5 equal fractions. Margin and isodose schemes differed between sites, but were chosen to assure lumpectomy cavity coverage, including a margin to account for potential microscopic disease and a small margin to account for residual uncertainty, and low doses to organs at risk. Patient setup methods varied between sites but were devised to assure reproducibility and optimal beam delivery angles. Radiation was delivered while tracking and correcting for respiratory motion with the Synchrony respiratory motion management system.
Results: Mean follow-up was 31 months (range, 6-57 months) at Swedish and median follow-up was 22 months (range, 7-39 months) at Winthrop. Local control was obtained and continues in all patients. One patient reported minor pain at the lumpectomy site 10 months post-treatment, a second had palpable, non-painful firmness at the lumpectomy site, and a single patient showed Grade 1 dry skin desquamation. No serious toxicity has been observed. The cosmesis was good-excellent in all 46 patients using the Harvard cosmesis scale.
Conclusions: CyberKnife SBRT/APBI appears safe with low toxicity and excellent short-term local control. Centers interested in CyberKnife SBRT/APBI for their patients should consider treating on protocol in Investigational Review Board-approved studies, or at least according to the American Society for Radiation Oncology (ASTRO) eligibility guidelines for women with early-stage breast cancer.
