The largest report to date of patients with breast cancer treated with accelerated partial breast irradiation (APBI) via multicatheter interstitial brachytherapy has found the treatment “resulted in excellent long-term local control and cosmesis outcomes.”1

The study, published in Annals of Surgical Oncology, provides much-needed data pending results of two ongoing long-term phase 3 randomized trials being conducted by the US National Surgical Adjuvant Breast and Bowel Program (NSABP) and the Groupe Européen de Curiethérapie (GEC)–European Society for Radiotherapy & Oncology (ESTRO), which are comparing conventional whole breast irradiation (WBI) to partial breast irradiation for women with stage 0, 1, or 2 breast cancer.

Adjuvant radiation following lumpectomy is considered standard breast-conservation therapy. Typically, WBI is delivered to the whole breast over 5 to 7 weeks, although recent data have shown good outcomes for 3 weeks of treatment. Drawbacks to WBI include lung and heart radiation exposure and patient noncompliance.

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Is targeting the entire breast necessary to the success of adjuvant radiotherapy? This was the question Mitchell Kamrava, MD, of the Department of Radiation Oncology at the University of California, Los Angeles (UCLA) in Los Angeles, CA, and colleagues from a cooperative group of institutions sought to answer about APBI, which “allows for a 1-week course of treatment focused on the highest area at risk of recurrence,” using data from the Pooled Registry of Multicatheter Interstitial Sites (PROMIS).

“There is controversy regarding who is the ideal candidate for partial breast irradiation outside of a clinical trial,” Dr. Kamrava told Cancer Therapy Advisor.

“There are guidelines from multiple organizations to help provide consensus until the randomized data is published. In general, women greater than 50 years [of age], tumors less than 3 cm, node negative, negative margins, and no previous chemotherapy may be candidates for partial breast radiation.”

The PROMIS registry dates to 1992, when coauthor Robert R. Kuske, MD, of Arizona Breast Cancer Specialists in Scottsdale, AZ, began treating patients with APBI.

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From 1992 to 2013, the cooperative group institutions—Arizona Breast Cancer Associations, the University of Wisconsin, William Beaumont Hospital, Gamma West Cancer Services, and UCLA—treated a total of 1,356 patients with multicatheter APBI.

The study examined 1,131 patients for whom follow-up data of more than 1 year were available and oncologic and cosmesis outcomes could be assessed. Median age was 59 (range, 22 to 90).