Interstitial High Dose Rate (HDR) Brachytherapy for Early Stage Breast Cancer: Five Year Follow-up of 168 Cases using Multi-catheter Technique

Abstract

External Beam Radiation Therapy (EBRT) has been the standard of care for breast conservation radiation therapy. Recent data indicates that Interstitial Implant and High Dose Rate (HDR) radiation afterloading compares very favorably to EBRT in selected patients. Patients with Tis, T1, and T2 tumors measuring ≤3 cm, negative surgical margins, and negative 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 the Anderson-Nair Template using from 3 to 8 planes, and 8 to 62 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 cm3 to 359 cm3. HDR treatment was given using the Nucletron afterloading system. The breast implant volume received 3,400 cGy in 10 fractions prescribed to the Planning Target Volume, given BID over 5 days. Between 2000 and 2008, 168 patients underwent Interstitial HDR Implant. The procedure was well tolerated. No patient required hospital admission. With a median follow-up 60 months (range, 6-98 months), local recurrence occurred in 3.6% (6/168). Cosmetic results were good to excellent in 88.1% (148/168) of the patients. There were no infections. Wound healing complications developed in 4.8% (8/168). Three of these patients had received anthracycline based Chemotherapy. The other five had large (>200 cm3) implant volumes, catheter spacing of 1.5 cm, and V-150% of >30%. Two patients healed after 6 months of conservative treatment. Surgery was required in 6 patients who developed fat necrosis. With median 60 month follow-up, 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 anthracycline based Chemotherapy, large (>200 cm3) implant volumes, and V-150% >30%, 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.