Interstitial High-Dose-Rate Brachytherapy for Ductal Carcinoma In Situ of the Breast: Median 6-Year Results of 59 Cases Using Multi-Catheter Technique

Abstract

Purpose: External beam radiation therapy (EBRT) has been the standard of care for breast conservation radiation therapy, in both invasive ductal carcinoma (IDC) and ductal carcinoma in situ (DCIS). Recent data indicate that interstitial implant and high-dose-rate (HDR) radiation afterloading compares very favorably to EBRT in selected cases of IDC. There are little data regarding HDR in DCIS. We report our HDR results in 59 patients with DCIS. Materials and Methods: 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 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 (Nucletron B.V., Veenendaal, The Netherlands). Treatment volumes ranged from 25 cm3 to 359 cm3. 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 2009, 251 patients underwent interstitial HDR implant. The procedure was well tolerated. No patient required hospital admission. With a median followup 72 months (range 6-120 months), local recurrence occurred in 4.0% (10/251). LR occurred in 3.6% (7/192) of patient with IDC vs. 5.1% (3/59) in DCIS (p = 0.70). Cosmetic results were good to excellent in 89.2% (224/251) of the patients. There were no infections. Wound healing complications developed in 3.2% (8/251). 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 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. There was no difference in LR between patients with IDC and DCIS. 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.