Outcomes in women treated with MammoSite brachytherapy or whole breast irradiation stratified by ASTRO Accelerated Partial Breast Irradiation Consensus Statement Groups.
OBJECTIVE
The American Society for Radiation Oncology published a Consensus Statement for accelerated partial breast irradiation identifying three groups: Suitable, Cautionary, and Unsuitable. The objective of this study was to compare oncologic outcomes in women treated with MammoSite brachytherapy (MB) vs. whole breast irradiation (WBI) after stratification into Statement groups.


METHODS
Eligible women had invasive carcinoma or ductal carcinoma in situ (DCIS) ≤ 3 cm, and ≤ 3 lymph nodes positive. Women were stratified by radiation modality and Statement groups. Survival analysis methods including Kaplan-Meier estimation, Cox regression, and competing risks analysis were used to assess overall survival (OS), disease-free survival (DFS), time to local failure (TTLF), and tumor bed failure (TBF).


RESULTS
A total of 459 (183 MB and 276 WBI) patients were treated from 2002 to 2009. After a median follow-up of 45 months, we found no statistical differences by stratification group or radiation modality with regard to OS and DFS. At 4 years TTLF or TBF were not statistically different between the cohorts. Univariate analysis in the MB cohort revealed that nodal positivity (pN1 vs. pN0) was related to TTLF (hazard ratio 6.39, p = 0.02). There was a suggestion that DCIS histology had an increased risk of failure when compared with invasive ductal carcinoma (hazard ratio 3.57, p = 0.06).


CONCLUSIONS
MB and WBI patients stratified by Statement groups seem to combine women who will have similar outcomes regardless of radiation modality. Although outcomes were similar, we remain guarded in overinterpretation of these preliminary results until further analysis and long-term follow-up data become available. Caution should be used in treating women with DCIS or pN1 disease with MB.
Department of Radiation Oncology, Medical University of South Carolina, Charleston, SC 29425, USA. zauls@musc.edu
A Jason
AJ
Zauls
John M
JM
Watkins
Amy E
AE
Wahlquist
N Craig
NC
Brackett
Eric G
EG
Aguero
Megan K
MK
Baker
Joseph M
JM
Jenrette
Elizabeth
E
Garrett-Mayer
Jennifer L
JL
Harper
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001365:Axilla; D001918:Brachytherapy / Q000379:methods; D001943:Breast Neoplasms / Q000145:classification / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D018270:Carcinoma, Ductal, Breast / Q000145:classification / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000145:classification / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary; D017024:Chemotherapy, Adjuvant; D032921:Consensus; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008207:Lymphatic Metastasis; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000401:mortality; D018787:Radiation Oncology; D018570:Risk Assessment / Q000379:methods; D016019:Survival Analysis; D013997:Time Factors; D017211:Treatment Failure