Accelerated partial breast irradiation with low-dose-rate interstitial implant brachytherapy after wide local excision: 12-year outcomes from a prospective trial.

PURPOSE: To evaluate the long-term toxicity, cosmesis, and local control of accelerated partial breast irradiation with implant brachytherapy after wide local excision for Stage T1N0 breast cancer (BCa).
MATERIALS AND METHODS: Between 1997 and 2001, 50 patients with Stage T1N0M0 BCa were treated in a Phase I-II protocol using low-dose-rate accelerated partial breast irradiation with implant brachytherapy after wide local excision and lymph node surgery. The total dose was escalated in three groups: 50 Gy (n = 20), 55 Gy (n = 17), and 60 Gy (n = 13). Patient- and physician-assessed breast cosmesis, patient satisfaction, toxicity, mammographic abnormalities, repeat biopsies, and disease status were prospectively evaluated at each visit. Kendall's tau (τ(β)) and logistic regression analyses were used to correlate outcomes with dose, implant volume, patient age, and systemic therapy.
RESULTS: The median follow-up period was 11.2 years (range, 4-14). The patient satisfaction rate was 67%, 67% reported good-excellent cosmesis, and 54% had moderate-severe fibrosis. Higher dose was correlated with worse cosmetic outcome (τ(β) 0.6, p < .0001), lower patient satisfaction (τ(β) 0.5, p < .001), and worse fibrosis (τ(β) 0.4, p = .0024). Of the 50 patients, 35% had fat necrosis and 34% developed telangiectasias ≥1 cm(2). Grade 3-4 late skin and subcutaneous toxicities were seen in 4 patients (9%) and 6 patients (13%), respectively, and both correlated with higher dose (τ(β) 0.3-0.5, p ≤ .01). One patient had Grade 4 skin ulceration and fat necrosis requiring surgery. Mammographic abnormalities were seen in 32% of the patients, and 30% underwent repeat biopsy, of which 73% were benign. Six patients had ipsilateral breast recurrence: five elsewhere in the breast, and one at the implant site. One patient died of metastatic BCa after recurrence. The 12-year actuarial local control, recurrence-free survival, and overall survival rate was 85% (95% confidence interval, 70-97%), 72% (95% confidence interval, 54-86%), and 87% (95% confidence interval, 73-99%), respectively.
CONCLUSION: Low-dose-rate accelerated partial breast irradiation with implant brachytherapy provides acceptable local control in select early-stage BCa patients. However, treatment-related toxicity and cosmetic complications were significant with longer follow-up and at higher doses.