The American Society for Radiation Oncology (ASTRO) issued a consensus statement in 2009 regarding patient selection for accelerated partial breast irradiation (APBI) following breast-conserving surgery (BCS) for breast cancer (BC). We reviewed our single-institution experience with APBI in patients considered “cautionary” by ASTRO to determine patterns of recurrence.

An institutional review board-approved, retrospective chart review was conducted from January 2004 to November 2009. We identified 106 “cautionary” patients with 109 BC. All patients were treated with BCS followed by APBI via balloon catheter brachytherapy. “Cautionary” criteria include patients aged 50–59 years, tumor size 2.1–3.0 cm, close margins (<2 mm), focal lymphovascular invasion, estrogen receptor (ER)-negative tumors, invasive lobular carcinoma, or ductal carcinoma in situ (DCIS) ≤ 3 cm. Rates of recurrence at any site were evaluated.

Median follow-up was 3 years. There were 3 IBTR (2.8%) at a median of 3.2 years. The 3-year actuarial IBTR rate was 1.8%. Patients with ER-negative invasive cancers had a higher IBTR rate compared with ER-positive patients (11.8% vs. 2.2%), although this did not reach statistical significance (P = 0.18). There were no IBTR in 46 patients with DCIS. On univariate analysis, there was no association between “cautionary” criteria and risk of local, regional, or distant recurrence.

Patients considered “cautionary” for APBI based on ASTRO guidelines had low rates of IBTR. ER-negative patients trended toward a higher IBTR rate with APBI compared with ER-positive patients. Longer follow-up is needed to establish the safety of APBI in “cautionary” patients.