Long-term outcomes of breast cancer patients receiving adjuvant accelerated partial breast irradiation (APBI) after breast-conserving surgery show excellent tumor control and cosmetic outcomes with minimal late toxicity, according to a new study.

APBI delivers highly conformal radiation therapy, during a period of 1 to 2 weeks, to the site where the cancer was removed. APBI has seen a tenfold increase in use from 2002 to 2007 and is currently the focus of several ongoing phase 3 trials. 

The University of Pittsburgh Cancer Institute study examined the long-term outcomes (over 5 years), tumor control, and breast cosmesis of a cohort of early-stage and ductal carcinoma in situ (DCIS) breast cancer patients who received a 5-day treatment of APBI at the University of Pittsburgh between 2002 and 2007. This study was published in the International Journal of Radiation Oncology ● Biology ● Physics (2014;88[2]:285-291).

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The study retrospectively reviewed 157 patients with localized breast cancer who were treated with adjuvant MammoSite, single-lumen balloon-based brachytherapy after breast-conserving surgery between June 1, 2002, and December 31, 2007. For all patients, at least 5 years had passed since receiving brachytherapy. Patients were all 40 years and older, with 88.5% older than 50 years. Patients were also categorized by demographics and tumor characteristics into suitable, cautionary, and unsuitable groups based on recommendations from American Society for Radiation Oncology’s (ASTRO’s) APBI Consensus Statement. 

APBI was delivered to a median dose of 34 Gy in 10 fractions over a 5-day period. In addition, 89% of patients received additional adjuvant systemic therapy, with 66.9% receiving hormonal therapy, 13.4% receiving chemotherapy, and 8.3% receiving chemotherapy with hormonal therapy.

Follow-up was conducted every 3 to 4 months for the first 2 years posttreatment, and every 6 months thereafter at the discretion of the patient’s breast surgeon and radiation oncologist. Baseline mammograms were performed 3 to 6 months after treatment, and annually thereafter. In addition, cosmetic outcomes were documented via photography at each visit, and toxicity was assessed during the final follow-up visit. 

At a median follow-up of 5.5 years posttreatment, the 5-year and 7-year actuarial ipsilateral breast control were 98%/98%, the lymph nodal control were 99%/98%, and the distant control were 99%/99%, respectively. The breast cancer-specific survival was 100% at 5 years and 99% at 7 years. The overall survival was 89% at 5 years and 86% at 7 years. There were no significant differences in tumor recurrence or survival rates in the appropriateness subgroups based on ASTRO’s consensus statement. Good to excellent breast cosmesis was reported in 93.4% of patients.

Overall toxicity rates were low, and the most common toxicity—telangiectasia—which is small, dilated blood vessels near the surface of the skin, was reported in 27% of study participants. The study correlated telangiectasia development and the maximum radiation dose to the skin. The study institution practice is to keep maximum skin dose at 100% or less; and at maximum, no more than 125% to limit the risk of telangiectasia.