AUTHOR=Vermeulen Sandra , Cotrutz Cristian , Buchanan Claire , Dawson Patricia , Morris Astrid , Porter Bruce , Meier Robert 

TITLE=Accelerated Partial Breast Irradiation: Using the CyberKnife as the Radiation Delivery Platform in the Treatment of Early Breast Cancer

JOURNAL=Frontiers in Oncology

VOLUME=1

YEAR=2011

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2011.00043

DOI=10.3389/fonc.2011.00043

ISSN=2234-943X

ABSTRACT=<p>We evaluate the CyberKnife (Accuray Incorporated, Sunnyvale, CA, USA) for non-invasive delivery of accelerated partial breast irradiation (APBI) in early breast cancer patients. Between 6/2009 and 5/2011, nine patients were treated with CyberKnife APBI. Normal tissue constraints were imposed as outlined in the National Surgical Adjuvant Breast and Bowel Project B-39/Radiation Therapy Oncology Group 0413 (NSABP/RTOG) Protocol (Vicini and White, <xref ref-type="bibr" rid="B27">2007</xref>). Patients received a total dose of 30 Gy in five fractions (group 1, <italic>n</italic> = 2) or 34 Gy in 10 fractions (group 2, <italic>n</italic> = 7) delivered to the planning treatment volume (PTV) defined as the clinical target volume (CTV) +2 mm. The CTV was defined as either the lumpectomy cavity plus 10 mm (<italic>n</italic> = 2) or 15 mm (<italic>n</italic> = 7). The cavity was defined by a T2-weighted non-contrast breast MRI fused to a planning non-contrast thoracic CT. The CyberKnife Synchrony system tracked gold fiducials sutured into the cavity wall during lumpectomy. Treatments started 4–5 weeks after lumpectomy. The mean PTV was 100 cm<sup>3</sup> (range, 92–108 cm<sup>3</sup>) and 105 cm<sup>3</sup> (range, 49–241 cm<sup>3</sup>) and the mean PTV isodose prescription line was 70% for groups 1 and 2, respectively. The mean percent of whole breast reference volume receiving 100 and 50% of the dose (<italic>V</italic><sub>100</sub> and <italic>V</italic><sub>50</sub>) for group 1 was 11% (range, 8–13%) and 23% (range, 16–30%) and for group 2 was 11% (range, 7–14%) and 26% (range, 21–35.0%), respectively. At a median 7 months follow-up (range, 4–26 months), no acute toxicities were seen. Acute cosmetic outcomes were excellent or good in all patients; for those patients with more than 12 months follow-up the late cosmesis outcomes were excellent or good. In conclusion, the lack of observable acute side effects and current excellent/good cosmetic outcomes is promising. We believe this suggests the CyberKnife is a suitable non-invasive radiation platform for delivering APBI with achievable normal tissue constraints.</p>