Outcomes Following Accelerated Partial Breast Irradiation in ASTRO Consensus Statement Unsuitable Patients.

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Abstract Purpose/Objective: There are limited data to guide patient selection for accelerated partial breast irradiation (APBI). In the recent ASTRO consensus statement, an unsuitable group was defined for whom APBI should only be offered in the context of a clinical trial. In this analysis, we reviewed the outcomes in this cohort of potentially higher risk patients.Materials/Methods: Between 2/2001 and 6/2006, a total of 322 consecutive patients were treated with HDR APBI at the University of Wisconsin. A total of 107 “unsuitable” patients were identified: 80 pts (74.7%) age < 50, 19 pts (17.8%) node positive, 20 pts (18.7%) with LVSI, 3 pts (2.8%) with tumors > 3 cm, and 2 pts (1.9%) with multifocal disease. 17 pts (15.9%) had multiple unsuitable features. In addition, 53 pts (49.5%) possessed “cautionary” features, including 19 pts (17.8%) ER negative and 10 pts (9.3%) with pure DCIS. The median age at diagnosis was 47 (range 25 – 84). All patients received 32 – 34 Gy in 8 - 10 bid fractions using multicatheter (93.5%) or Mammosite balloon (6.5%) HDR brachytherapy.Results: With a median follow-up of 60 months (range 1.1 - 97.8 months), there were 8 loco-regional recurrences (3 local only, 2 regional and 3 loco-regional and distant). Four of 5 patients without distant disease were successfully salvaged and had no evidence of disease at last follow-up. The 6 yr actuarial loco-regional control rate is 91.3% +/- 5.9%, with a latency to recurrence ranging from 10 – 41 months. The 6 yr disease free survival for the entire cohort is 89%, with a cause-specific survival and overall survival of 92.5% and 89%, respectively. There were no loco-regional recurrences observed among those with age < 50 without other unsuitable (LVSI, node +, > 3 cm, multifocality) or cautionary (ER -, EIC, tumor 2 – 3 cm, lobular histology, DCIS, < 2 mm margins) features (n = 31). In comparison, the loco-regional recurrence rate is 12.3% for those deemed unsuitable by virtue of surgical and pathologic factors (p = .064). Loco-regional recurrences were observed in 2/19 node positive pts, 3/20 pts with LVSI, 1/2 pts with multifocal disease, 2/34 with age < 50 alone and cautionary features, and 0/3 pts with tumors > 3 cm.Conclusions: Currently, uncertainty exists regarding patient selection for APBI. Based upon the observed local recurrence rates in the current analysis and the well-established benefits of whole breast radiotherapy, we continue to encourage clinical trial participation among this cohort of patients, specifically RTOG 0412/NSABP B-39. Although not statistically significant, the absence of local failures among women < 50 yrs without adverse histopathologic features suggests they may be appropriate candidates for APBI. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 955.