Interstitial High Dose Rate (HDR) Brachytherapy for Ductal Carcinoma In Situ of the Breast: Median 6 Year Results of 63 Cases using Multi-catheter Technique

Abstract

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 indicates that Interstitial Implant and High Dose Rate (HDR) radiation afterloading compares very favorably to EBRT in selected cases of IDC. There is little data regarding HDR in DCIS. We report our HDR results in 63 patients with DCIS. 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 with a custom designed template using from 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 cm3 to 359 cm3. HDR treatment was given using the Nucletron afterloading system. The breast implant volume received 3400 c Gy in 10 fractions prescribed to the Planning Target Volume, given BID over 5 days. Between 2000 and 2010, 268 patients underwent Interstitial HDR Implant. The procedure was well tolerated. No patient required hospital admission. With a median follow-up 72 months (range, 6-128 months), local recurrence (LR) occurred in 3.7% (10/268). LR occurred in 3.5% (7/205) of patient with IDC vs. 4.8% (3/63) in DCIS (p = 0.70). Cosmetic results were good to excellent in 89.5% (240/268) of the patients. There were no infections. Wound healing complications developed in 3.0% (8/268). 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. With median 72 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. 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.