Results of a retrospective population-based cohort study [JAMA. 2012;307(17):1827-1837] show that older women with breast cancer treated with brachytherapy compared with whole-breast irradiation (WBI) have worse outcomes in terms of less long-term breast preservation and increased complications without any difference in survival.
A growing number of women with breast cancer are undergoing brachytherapy following lumpectomy, yet evidence from randomized trials comparing brachytherapy to the standard treatment with WBI are not yet available. The current study was undertaken to help guide treatment decisions during this interim period between the increasing use of brachytherapy and the still unavailable randomized evidence on how it compares to WBI.
Using national Medicare data, the study included 92,735 women ≥67 years of age diagnosed with invasive breast cancer between 2003 and 2007 and treated with lumpectomy followed by brachytherapy (n=6952) or WBI (n=85,783). Women were excluded from the study if they had only 1 diagnosis of breast cancer, metastatic disease at diagnosis, a history of breast cancer, noncontinuous Medicare Part A and B coverage within 12 months before and after diagnosis, unconfirmed treatment with radiation, treatment with both external beam radiation and brachytherapy, and if they did not receive at least 11 fractions of radiation.
Using mastectomy as an indicator of the failure to preserve the breast, the study compared the cumulative incidence and adjusted risk of mastectomy after treatment with either brachytherapy or WBI. The study also compared the short- and long-term incidence of complications between the 2 treatments as well as overall survival.
The study found worse outcomes in the women treated with brachytherapy versus those treated with WBI, with a significantly higher 5-year incidence of subsequent mastectomy in women treated with brachytherapy (3.95%; 95% confidence interval [CI], 3.19%-4.88%) compared with WBI (2.18%; 95% CI, 2.04%-2.33%; P<.001).
Brachytherapy remained associated with an increased risk of mastectomy on multivariate analysis, with a hazard ratio (HR) of 2.19 (95% CI, 1.84-2.61; P<.001). A borderline significant finding was found for patients with axillary lymph node involvement and radiation type (P=.05), indicating that patients with involved nodes treated with brachytherapy were particularly at high risk of subsequent mastectomy compared to those treated with WBI (HR, 5.08; 95% CI, 2.94-8.80; P<.001).
Brachytherapy was also associated with more frequent complications than WBI, including more frequent postoperative infectious (16.20% vs 10.33%, P<.001) and noninfectious (16.25% vs 9.00%, P<.001) complications, and higher 5-year incidence of breast pain (14.55% vs 11.92%, P<.001), fat necrosis (8.26% vs 4.05%, P<.001), and rib fracture (4.53% vs 3.62%, P≤.01).
No difference in 5-year survival was found between brachytherapy (87.66%; 95% CI, 85.94%-89.19%) and WBI (87.04%; CI, 86.69%-87.39%), with an adjusted HR of 0.94 (95% CI, 0.84-1.05; P=.26).
Stating that these results are awaiting validation from prospective randomized trials, the investigators emphasize that until validation is available, these results “prompt caution over widespread application of breast brachytherapy outside the study setting.”
Limitations include the fact that the study population was restricted to only older patients with a relatively short follow-up, the potential for misclassification bias of the definitions used for invasive cancer and radiation based on claims data, the inability to adjust for disease covariates, the potential of detection bias affecting complication outcomes, and the possibility that the outcome measure based on subsequent mastectomy could have been a marker for local tumor recurrence or treatment-related complications.