Association between treatment with brachytherapy vs whole-breast irradiation and subsequent mastectomy, complications, and survival among older women with invasive breast cancer

Abstract

Context: Brachytherapy is a radiation treatment that uses an implanted radioactive source. In recent years, use of breast brachytherapy after lumpectomy for early breast cancer has increased substantially despite a lack of randomized trial data comparing its effectiveness with standard whole-breast irradiation (WBI). Because results of long-term randomized trials will not be reported for years, detailed analysis of clinical outcomes in a nonrandomized setting is warranted.

Objective: To compare the likelihood of breast preservation, complications, and survival for brachytherapy vs WBI among a nationwide cohort of older women with breast cancer with fee-for-service Medicare.

Design: Retrospective population-based cohort study of 92,735 women aged 67 years or older with incident invasive breast cancer, diagnosed between 2003 and 2007 and followed up through 2008. After lumpectomy 6952 patients were treated with brachytherapy vs 85,783 with WBI.

Main outcome measures: Cumulative incidence and adjusted risk of subsequent mastectomy (an indicator of failure to preserve the breast) and death were compared using the log-rank test and proportional hazards models. Odds of postoperative infectious and noninfectious complications within 1 year were compared using the χ(2) test and logistic models. Cumulative incidences of long-term complications were compared using the log-rank test.

Results: Five-year incidence of subsequent mastectomy was higher in women treated with brachytherapy (3.95%; 95% CI, 3.19%-4.88%) vs WBI (2.18%; 95% CI, 2.04%-2.33%; P < .001) and persisted after multivariate adjustment (hazard ratio [HR], 2.19; 95% CI, 1.84-2.61, P < .001). Brachytherapy was associated with more frequent infectious (16.20%; 95% CI, 15.34%-17.08% vs 10.33%; 95% CI, 10.13%-10.53%; P < .001; adjusted odds ratio [OR], 1.76; 1.64-1.88) and noninfectious (16.25%; 95% CI, 15.39%-17.14% vs 9.00%; 95% CI, 8.81%-9.19%; P < .001; adjusted OR, 2.03; 95% CI, 1.89-2.17) postoperative complications; and higher 5-year incidence of breast pain (14.55%, 95% CI, 13.39%-15.80% vs 11.92%; 95% CI, 11.63%-12.21%), fat necrosis (8.26%; 95% CI, 7.27-9.38 vs 4.05%; 95% CI, 3.87%-4.24%), and rib fracture (4.53%; 95% CI, 3.63%-5.64% vs 3.62%; 95% CI, 3.44%-3.82%; P ≤ .01 for all). Five-year overall survival was 87.66% (95% CI, 85.94%-89.18%) in patients treated with brachytherapy vs 87.04% (95% CI, 86.69%-87.39%) in patients treated with WBI (adjusted HR, 0.94; 95% CI, 0.84-1.05; P = .26).

Conclusion: In a cohort of older women with breast cancer, treatment with brachytherapy compared with WBI was associated worse with long-term breast preservation and increased complications but no difference in survival.

Figure 1

Patients Treated With Brachytherapy Percentage of patients were treated with brachytherapy relative to the total number of patients treated with either brachytherapy or whole-breast irradiation following lumpectomy for invasive breast cancer (P for trend, <.001). Error bars indicate 95% confidence intervals.

Figure 2

Cumulative Incidence of Subsequent Mastectomy The difference in risk was significant (P<.001, log-rank). Error bars indicate 95% confidence intervals.

Figure 3

Frequency of Infectious and Noninfectious Postoperative Complications Patients treated with brachytherapy experienced higher unadjusted risks of infectious (odds ratio [OR], 1.82; 95% CI, 1.70–1.95; P<.001) and noninfectious (OR, 1.90; 95% CI, 1.77–2.04; P<.001) complications when analyzed by the 30-day interval through 18 months after diagnosis than women treated with whole-breast irradiation (ORs and P values were derived from generalized estimating equation). Error bars indicate 95% confidence intervals.