Outcome of a phase II prospective study on partial breast irradiation with interstitial multi-catheter high-dose-rate brachytherapy.

Background and Purpose: Partial breast irradiation (PBI) is an alternative to whole-breast irradiation after breast-conserving surgery in selected patients. Until the results of randomized phase III studies are available, phase II studies inform about PBI. We report the 5 year results of a phase II prospective study with PBI using interstitial multi-catheter high-dose-rate brachytherapy (ClinicalTrials.gov Identifier: NCT00499057).
Methods: Hundred patients received PBI (4 Gy, twice a day for 4 days, until 32 Gy). Inclusion criteria were: age ≥ 40years, infiltrating carcinoma without lobular histology, ductal in situ carcinoma, tumor size ≤ 2.5 cm, negative surgical margins and axillary lymph nodes.
Results: At a median follow-up of 60 months late toxicity occurred in 25 patients; the 5-year probability of freedom from late toxicity was 72.6% (95% CI: 63.7-81.7). Tamoxifen was the only significant risk factor for late toxicity. Cosmetic results, judged by physicians and patients, were good/excellent in 98 patients. Three local relapses (1 true, 2 elsewhere) and 1 regional relapse occurred. The 5-year probability of local or regional relapse-free survival was 97.7% (95% CI: 91.1-99.4) and 99.0% (95% CI: 92.9-99.8), respectively.
Conclusion: PBI with interstitial multi-catheter brachytherapy is associated with low relapse and late toxicity rates.
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