A Multi-institutional Study of Implementation, Tolerance and Early Clinial Results With Non-invasive Image-Guided Breast Brachytherapy for Tumor Bed Boost

Abstract

interstitial implant and High-dose-rate (HDR) radiation afterloading compares very favorably to EBRT in selected patients. We report median 6 year followup in 273 cases. Materials andMethods: Patients with Tis, T1, and T2 tumors measuring# 4 cm, negative surgical margins, and#3 axillary lymph nodes were judged to be candidates for interstitial implant. Implants were performed under stereotactic mammographic guidance with conscious sedation and local anesthesia. The implants were placed using a custom designed template with 3 to 8 planes, and 8 to 74 needles. Catheters were subsequently threaded thru the needles, and the needles removed. Catheter spacing was 1.0 to 1.5 cm. Radiation treatment planning was performed using CT scanning and the Plato System. Treatment volumes ranged from 25 cm to 458 cm. HDR treatment was given using the Nucletron afterloading system. The breast implant volume received 3400 cGy in 10 fractions prescribed to the planning target volume, given BID over 5 days. Results: Between 2000 and 2010, 273 patients underwent interstitial HDR implant. The procedure was well tolerated. No patient required hospital admission. With a median followup 72 months (range 6e132 months), local recurrence occurred in 4.0% (11/273). Cosmetic results were good to excellent in 89.0% (243/273) of the patients. There were no infections. Wound healing complications developed in 2.9% (8/273). Three of these patients had received anthracycline based Chemotherapy. The other five had large (O200 cm) implant volumes. In patients with catheter spacing of 1.5 cm and V-150% O30%, 9.5% (8/84) developed wound complications vs. 0% (0/189) in patients with catheter spacing of 1.0 cm and V-150% !30% (p 5 0.0001). Two patients healed after 6 months of conservative treatment. Surgery was required in six patients who developed fat necrosis. Conclusions: With median 72-month followup, breast conservation radiation therapy utilizing interstitial multi-catheter HDR implant has yielded local recurrence rates and cosmetic results which compare favorably to EBRT in selected patients. Treatment with anthracyclinebased chemotherapy, large (O200 cm) implant volumes, and V-150% O30%, appear to be relative contraindications to interstitial HDR implant. Finally, catheter spacing of 1 cm yielded optimal dosimetry and minimized complications. Compared to MammoSite technique, the interstitial multi-catheter method offers greater flexibility of radiation delivery. Advantages, include no concern regarding surgical cavity shape irregularities, balloon conformality to surgical cavity, balloon rupture, balloon movement, air gaps, skin balloon proximity to skin, balloon shape distortion, and catheter movement within the balloon.