Outcomes of Breast Cancer Patients Treated with Accelerated Partial Breast Irradiation Via Multicatheter Interstitial Brachytherapy: The Pooled Registry of Multicatheter Interstitial Sites (PROMIS) Experience.
OBJECTIVE
To report outcomes for breast-conserving therapy using adjuvant accelerated partial breast irradiation with interstitial multicatheter brachytherapy by a cooperative group of institutions.


METHODS
From 1992 to 2013, a total of 1356 patients were treated with breast-conserving surgery and adjuvant accelerated partial breast irradiation using interstitial multicatheter brachytherapy. A total of 1131 patients had >1 year of data available to assess oncologic and cosmesis outcomes. Median age was 59 years old (range 22-90 years). Histologies treated included 1005 (73 %) invasive ductal carcinoma and 240 (18 %) ductal carcinoma-in situ. T stages were 18 % Tis, 75 % T1, and 8 % ≥T2. Nodal status was 73 % N0 and 6 % N1a. Estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 was positive in 83, 70, and 6 %, respectively. Cox multivariate analysis for local control was performed using histology, age, estrogen receptor status, tumor size, grade, margin, and nodal status.


RESULTS
The mean (SD) follow-up was 6.9 years (4.3). The 10-year actuarial risk (95 % confidence interval) of an ipsilateral breast tumor recurrence was 7.6 % (5.6-10.1). Other 10-year actuarial risks (95 % confidence interval) were regional failure 2.3 % (1.4-3.7), distant metastasis 3.8 % (2.5-5.7), cause-specific survival 96.3 % (94.2-97.6), overall survival 86.5 (83.0-89.3), and new contralateral cancers 4.6 % (3.0-6.9). On multivariate analysis, high grade (hazard ratio 2.81) and positive margin status (hazard ratio 18.42) were the only two significant variables associated with an increased risk of local recurrence. Physician-reported cosmesis was excellent/good in 84 % (98 of 116) of patients with >5 years of follow-up.


CONCLUSIONS
This is the largest report of outcomes with interstitial breast brachytherapy. This treatment resulted in excellent long-term local control and cosmesis outcomes.
Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA, USA. mkamrava@mednet.ucla.edu.
Mitchell
M
Kamrava
Arizona Breast Cancer Specialists, Scottsdale, USA.
Robert R
RR
Kuske
Department of Radiation Oncology, University of Wisconsin, Madison, USA.
Bethany
B
Anderson
Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, USA.
Peter
P
Chen
Gamma West Cancer Services, Salt Lake City, USA.
John
J
Hayes
Arizona Breast Cancer Specialists, Scottsdale, USA.
Coral
C
Quiet
Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA, USA.
Pin-Chieh
PC
Wang
Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA, USA.
Darlene
D
Veruttipong
Arizona Breast Cancer Specialists, Scottsdale, USA.
Margaret
M
Snyder
Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA, USA.
D
D
Jeffrey Demanes
D000328:Adult; D001918:Brachytherapy; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D018270:Carcinoma, Ductal, Breast / Q000473:pathology / Q000532:radiotherapy*; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000473:pathology / Q000532:radiotherapy*; D018275:Carcinoma, Lobular / Q000473:pathology / Q000532:radiotherapy*; D002404:Catheterization / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D060787:Neoplasm Grading; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local / Q000473:pathology / Q000532:radiotherapy*; D009367:Neoplasm Staging; D011379:Prognosis; D011879:Radiotherapy Dosage; D012042:Registries; D012189:Retrospective Studies; D015996:Survival Rate