Accelerated partial breast brachytherapy, involving temporarily placing a small radioactive source in the breast after lumpectomy, is an increasingly popular radiation treatment for older patients diagnosed with early stage breast cancer. The incidence of brachytherapy in the US increased from less than 1% in 2000 to 13% in 2007. However, despite this growing utilization, there is a lack of studies to compare its effectiveness and toxicity profile with standard whole breast irradiation. Grace Smith, MD, PhD (MD Anderson Cancer Center Houston, TX, USA) and colleagues evaluated the Medicare claims of all U.S. female beneficiaries (N=130,535) aged older than 66 years diagnosed with incident-invasive breast cancer between 2000 and 2007. Patients were treated with conservative surgery followed by accelerated partial breast brachytherapy alone (N=7,291) or whole-breast irradiation (N=123,244).
Four percent of patients treated with brachytherapy underwent a subsequent mastectomy compared to only 2.2% of patients treated with whole-breast irradiation. “We found that women treated with brachytherapy experience a two-fold increased risk for subsequent mastectomy, indicating that women treated with brachytherapy were more likely to lose their breast after their initial breast-conserving therapy,” said Smith. Furthermore, patients treated with brachytherapy also had a two-fold increased risk for postoperative infections (16% vs. 10%) and noninfectious (16% vs. 8%) complications compared with patients treated with whole breast irradiation. Moreover, compared to whole breast irradiation, women treated with brachytherapy were also more likely to experience radiation-related side effects, such as breast pain (15% vs. 12%), fat necrosis (9% vs. 4%) and rib fractures (4.2% vs. 3.6%).
The researchers however also noted the study’s limits, including that it was not randomised, the relatively short follow-up of patients (3.5 years) and the fact that limited details regarding tumor characteristics were available.
In her conclusion, Smith admitted to be shocked by these results. “I think that our results are very plausible and consistent with the literature,” she said. “However, I did not expect that a difference in outcomes between brachytherapy and whole-breast irradiation would be found using this claims-based approach.” These data underscore the importance of waiting for mature data from randomized clinical trials before widespread adoption of breast brachytherapy.