Background: Several phase III trials have demonstrated equivalent long-term survival between breast conserving surgery plus radiation therapy and mastectomy in patients with early-stage breast cancer but have not provided information on the optimal volume of breast tissue requiring post-lumpectomy radiation therapy. Therefore, we examined the 5-year results of a single institution's experience with radiation therapy limited to the region of the tumor bed (i.e., limited-field radiation therapy) in selected patients treated with breast-conserving therapy and compared them with results of matched breast-conserving therapy patients who underwent whole-breast radiation therapy.
Methods: A total of 199 patients with early-stage breast cancer were treated prospectively with breast-conserving therapy and limited-field radiation therapy using interstitial brachytherapy. To compare potential differences in local recurrence rates based on the volume of breast tissue irradiated, patients in the limited-field radiation therapy group were matched with 199 patients treated with whole-breast radiation therapy. Match criteria included tumor size, lymph-node status, patient age, margins of excision, estrogen receptor status, and use of adjuvant tamoxifen therapy. Local-regional control and disease-free and overall survival were analyzed using the Kaplan-Meier method, and the statistical significance of differences between treatment groups was calculated using the log-rank test. All statistical tests were two-sided.
Results: Median follow-up for surviving patients was 65 months (range = 12-115 months). Five ipsilateral breast failures (i.e., recurrences) were observed in patients treated with limited-field radiation therapy. The cumulative incidence of local recurrence was 1% (95% confidence interval [CI] = 0% to 2.8%). On matched-pair analysis, the rate of local recurrence was not statistically significantly different between the patient groups (1% [95% CI = 0% to 2.4%] for the whole-breast radiation therapy patients versus 1% [95% CI = 0% to 2.8%] for the limited-field radiation therapy patients; P =.65).
Conclusions: Limited-field radiation therapy administered to the region of the tumor bed has comparable 5-year local control rates to whole-breast radiation therapy in selected patients.