Interstitial high-dose-rate brachytherapy boost: The feasibility and cosmetic outcome of a fractionated outpatient delivery scheme

Purpose: To evaluate the feasibility, potential toxicity, and cosmetic outc ome of fractionated interstitial high dose rate (HDR) brachytherapy boost f or the management of patients with breast cancer at increased risk for loca l recurrence. Methods and Materials: From 1994 to 1996, 18 women,vith early stage breast cancer underwent conventionally fractionated whole breast radiotherapy (50- 50.4 Gy) followed by interstitial HDR brachytherapy boost. All were conside red to be at high risk for local failure. Seventeen had pathologically conf irmed final surgical margins of less than 2 mm or focally positive. Brachyt herapy catheter placement and treatment delivery were conducted on an outpa tient basis. Preplanning was used to determine optimal catheter positions t o enhance dose homogeneity of dose delivery. The total HDR boost dose was 1 5 Gy delivered in 6 fractions of 2.5 Gy over 3 days. Focal control, surviva l, late toxicities (LENT-SOMA), and cosmetic outcome were recorded in follo w-up. In addition, factors potentially influencing cosmesis were analyzed b y logistic regression analysis. Results: The minimum follow-up is 40 months with a median 50 months. Sixtee n patients were alive without disease at last follow-up. There have been no in-breast failures observed. One patient died with brain metastases, and a nother died of unrelated causes without evidence of disease. Grade 1-2 late toxicities included 39% with hyperpigmentation, 56% with detectable fibros is, 28% with occasional discomfort, and 11% with visible telangiectasias. G rade 3 toxicity was reported in one patient as persistent discomfort. Sixty -seven percent of patients were considered to have experienced good/excelle nt cosmetic outcomes. Factors with a direct relationship to adverse cosmeti c outcome were extent of surgical defect (p = 0.00001), primary excision vo lume (p = 0.017), and total excision volume (p = 0.015). Conclusions: For high risk patients who may benefit from increased doses, i nterstitial HDR brachytherapy provides a convenient outpatient method for b oosting the lumpectomy cavity following conventional whole breast irradiati on without overdosing normal tissues. The fractionation scheme of 15 Gy in 6 fractions over 3 days is well tolerated. The volume of tissue removed fro m the breast at lumpectomy appears to dominate cosmetic outcome in this gro up of patients. (C) 2000 Elsevier Science Inc.