Accelerated partial-breast brachytherapy linked to more toxicity than whole-breast irradiation

Issue: January 25, 2012

San Antonio Breast Cancer Symposium

SAN ANTONIO — Accelerated partial-breast brachytherapy was inferior to whole-breast irradiation and also was associated with increased acute and late toxicities, researchers from The University of Texas MD Anderson Cancer Center said here.

“Accelerated partial-breast brachytherapy is an increasingly popular radiation treatment for older patients diagnosed with early-stage breast cancer,” said Benjamin D. Smith, MD, assistant professor in the department of radiation oncology at MD Anderson Cancer Center. “Despite growing utilization, there is a lack of population-based cohort studies, as well as randomized phase 3 data, to compare its effectiveness and toxicity profile with standard whole-breast irradiation.”

The researchers used Medicare billing claims to identify patients aged older than 66 years with incident invasive breast cancer who were diagnosed between 2000 and 2007. The patients were treated with conservative surgery followed by accelerated partial-breast brachytherapy or whole-breast irradiation. The researchers compared the incidence of mastectomy between the groups, the risk for acute toxicities and the cumulative incidence of long-term toxicity.

In 130,535 women, the use of accelerated partial-breast brachytherapy increased from less than 1% of patients in 2000 to 13% of patients in 2007. These women were less likely to have axillary lymph node involvement and to have received chemotherapy, but were more likely to be older, white and have comorbidities.

At 5 years, the incidence of subsequent mastectomy was 4% in those treated with accelerated partial-breast brachytherapy vs. 2.2% in those treated with whole-breast irradiation (P<.001). Accelerated partial-breast brachytherapy also was associated with more acute complications, including a higher risk for hospitalization and infection. Accelerated partial-breast brachytherapy also was associated with a higher 5-year incidence of rib fracture, fat necrosis and breast pain, but a lower incidence of pneumonitis.

“These data underscore the importance of awaiting mature results of randomized trials designed to prospectively compare these treatments before employing widespread adoption of accelerated partial-breast brachytherapy as an alternative to whole-breast irradiation in select patients,” Smith said.

Disclosure: Dr. Smith reports no relevant financial disclosures.

Earn CME this spring at the HemOnc Today Breast Cancer Review & Perspective meeting to be held March 23-24, 2012 at the Hilton San Diego Bayfront. See details at HemOncTodayBreastCancer.com.

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Smith G. #S2-1. Presented at: the 2011 CTRC-AACR San Antonio Breast Cancer Symposium; Dec. 6-10, 2011; San Antonio.

This is the first study of this type that has looked at a larger population. There are several parts that are interesting. The recurrence rate is slightly higher in patients who had the partial-breast brachytherapy; however, the numbers are not huge. To go from a 2% rate to a 4% rate is still a low risk. It tells you that we need to have some prospective data, and hopefully, we will get that information soon with the NSAPB B39 study. To get that information is crucial before we open the Pandora’s box. Another interesting part of this study was the data on complications. Some of the complications continued, even up to 18 months afterward. It says we need to be particularly cautious in evaluating complications in people who are receiving this treatment now. However, the data were collected earlier in the time frame, so what we don’t know is whether there is a learning curve. Many people who were treated in this early part of the study time frame may have had more complications because we weren’t aware of these potential complications that may be prevented by paying attention to different subtleties in the techniques. These are exciting data, but it serves as a cautionary reminder that we need to think carefully when offering this treatment to a patient not in a study situation.

Ivy A. Petersen, MD
Associate Professor of Radiation Oncology, Mayo Clinic, Rochester, Minn.

Disclosure: Dr. Petersen reports no relevant financial disclosures.

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