108 Background: To evaluate the toxicity of multilumen breast brachytherapy in patients with 5 mm or less balloon surface-skin distance (BSD) treated with the Contura catheter. Methods: From September 2008 through February 2010 a total of 411 patients with early-stage breast cancer (stages 0, I, IIA) were treated with multilumen HDR brachytherapy for definitive APBI using the Contura brachytherapy catheter. Of those patients 92 had a balloon surface-skin distance (BSD) of 5 mm or less, with 6 months clinical follow-up. All patients received 34 Gy in 10 fractions bid over 5 days. The PTV_EVAL (cc) defined as a 1 cm expansion from the anterior surface of the device; BSD (mm) defined as the distance from the closest point on the balloon to the closet point on the skin surface; maximum skin dose (% and cGy); the volume of breast tissue (cc) receiving 150% and 200% of the prescription dose (V150, V200). Patient toxicity was evaluated at 1 week, 1 month, and 6 months following brachytherapy including; skin reaction (RTOG Acute Radiation Morbidity Scoring Criteria), pigmentation, telangiectasia, pain, fat necrosis, symptomatic seroma. Results: The mean BSD was 3.7 mm, with a range of 1-5 mm. The mean maximum skin dose was 4508 cGy (132.5%). The mean V150 was 21 cc and the V200 was 4.7 cc. The mean PTV_EVAL V90 was 93.7%. 49% of patients had skin reaction, including at 1 week; 47% Grade 1, 0% Grade 2 or 3. At 1 month; 31% Grade 1, 14% Grade 2 and 0% Grade 3. At 6 months; 2% Grade 1, 2% Grade 2 and 0% Grade 3. 6.5 % developed pigmentation changes (hypo or hyper). 5.4% developed telangiectasias, 9.7% reported pain. No patients had fat necrosis, and 15.2 % had a symptomatic seroma. 1 patient had wound dehiscence (maxium skin dose 4195 cGy, 123.4% of prescribed dose). Patients that experienced toxicity had no difference in BSD (3.6 vs 3.9 mm) or in the maximum skin dose (132.6% vs. 132.6%) compared to those that did not experience toxicity. Conclusions: Breast brachytherapy in patients with 5 mm or less BSD has acceptable toxicity with proper planning using the Contura multilumen catheter. Careful attention to maximum skin dose must be used, and we recommend not exceeding 145 % (4,930 cGy) of the prescribed dose.
The incidence of fat necrosis in balloon-based breast brachytherapy
