Ten-year results of a phase II study with a single fraction of high-dose-rate brachytherapy (FAST-boost) after whole breast irradiation in invasive breast carcinoma.

PURPOSE: We present the results of a prospective ten-year follow-up study to prove the effectiveness of a single fraction of 192-Ir high-dose-rate (HDR) brachytherapy (BT) as a boost. PATIENTS AND METHODS: Between 1999 and 2000, 84 consecutive patients with invasive breast carcinoma, with over 4 mm free margins after conservative surgery, were treated. All cases were stages T1-2, except for one case, a stage T3, 81% pN0, 19% pN1-2. Chemotherapy was used in 47% and hormonal therapy in 87%. Whole breast external beam radiotherapy (46 Gy) was followed 1-2 weeks later by an implant with metallic needles. A 7 Gy single dose of HDR BT to the 90% isodose line was delivered on an outpatient basis. Dosimetry was performed theoretically. This technique is called FAST-boost because the whole treatment is delivered in about two hours.
RESULTS: With a median follow-up of 120 months, three patients relapsed in the margin of the implant and two in a different quadrant (5/84, 6%). Actuarial local control at five and ten years was 98.5% and 95.6%. Overall survival was 92.7% and 90.2%, and disease-free survival 90.2% and 79.9%. Cosmetic results were good or excellent in 92.5%.
CONCLUSIONS: A single-fraction HDR boost with rigid needles (FAST-boost) is a good, quick, simple technique when surgical margins are free.