Phase 2 study of pre-excision single-dose intraoperative radiation therapy for early-stage breast cancers: six-year update with application of the ASTRO accelerated partial breast irradiation consensus statement criteria.
BACKGROUND
Intraoperative radiation therapy (IORT) allows delivery of high-dose radiation at the time of lumpectomy, potentially sparing adjuvant daily radiation. A phase 2 study of pre-excision IORT was performed for early-stage breast cancer.


METHODS
Patients ≥ 48 years of age with invasive ductal carcinoma, ≤ 3 cm, and clinically node-negative were eligible for this study, which was approved by institutional review board. Ultrasound was used to select electron energy and cone size to cover the tumor plus 1.5- to 2.0-cm lateral margins and 1-cm-deep margins (90% isodose). Fifteen Gy was delivered with a Mobetron irradiator, and immediate needle-localized partial mastectomy followed. Local event results were updated using the Kaplan-Meier method.


RESULTS
A total of 53 patients received IORT alone. Median age was 63 years, and median tumor size was 1.2 cm. Of these, 81% were positive for estrogen receptor or progesterone receptor, 11% were positive for human epidermal growth factor receptor 2, and 15% were triple-negative. Also, 42%, 49%, and 9% would have fallen into the Suitable, Cautionary, and Unsuitable groups, respectively, of the American Society of Therapeutic Radiation Oncology consensus statement for accelerated partial breast irradiation. Median follow-up was 69 months. Ipsilateral events occurred in 8 of 53 patients. The 6-year actuarial rate of ipsilateral events was 15% (95% confidence interval = 7%-29%). The crude event rate for Suitable and Cautionary groups was 1 of 22 (5%) and 7 of 26 (27%), respectively. Overall survival was 94.4%, and breast cancer-specific survival was 100%.


CONCLUSIONS
The rate of local events in this study is a matter of concern, especially in the Cautionary group. On the basis of these findings, pre-excision IORT, as delivered in this study, may not provide adequate local control for less favorable early-stage breast cancers.
Department of Radiation Oncology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
Noam A
NA
Vanderwalde
Ellen L
EL
Jones
Randall J
RJ
Kimple
Dominic T
DT
Moore
Nancy
N
Klauber-Demore
Carolyn I
CI
Sartor
David W
DW
Ollila
D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D007430:Intraoperative Care; D008875:Middle Aged