Abstract P5-14-16: Hypofractionated breast irradiation in early-stage breast cancer patients following adjuvant chemotherapy: Evaluation of acute and late toxicities

Abstract

Abstract Purpose To evaluate the effect of adjuvant chemotherapy (CTX) on acute and late toxicity among women undergoing hypofractionated radiation therapy (HRT) following breast-conserving therapy and to assess the relative impact of breast size. Materials and Methods In this retrospective study, patients treated with HRT to the whole breast (42.4 Gy in 16 fractions) followed by a boost (9.6 Gy in 4 fractions) between 2005 and 2009 were evaluated for inclusion. Early-stage (I-II) patients who underwent post-lumpectomy CTX prior to HRT were included. Patients who underwent neoadjuvant CTX were excluded; node positive patients and larger-breasted women (chest wall separation of >25 cm) were included. Toxicity evaluations during HRT and at 2-4 weeks, 3, 6, 9 months, and at yearly intervals were collected and graded using the RTOG Acute and Late Toxicity scales. Relevant data was available in 43 women. The median age was 60 years (35 – 71), and women were primarily of African American (55.8%) and Hispanic (27.9%) ethnicity. The majority of patients had high-grade lesions (69.8%), were Stage II (60.4%), and had T1 primaries (55.8%). Slightly more than half the patients (53.5%) were ER+; 20% were Her2 positive, and 37.2% were triple negative. Thirty-three (76.7%) were treated in the prone position. Lumpectomy cavity boosts were given via photons (58.2%) or electrons. Chemotherapy regimens included ACT (Adriamycin, Cytoxan, and Taxol) in 33/43 (76.7%) and CMF (Cytoxan, methotrexate, and 5FU) in the remainder. The median interval between completion of adjuvant CTX and the start of HRT was 41 days. The median BMI of the women was 31.8 (18.2 – 44.4; normal weight defined as BMI of 18.5 – 24.9); 11 women (25.6%) had a separation of more than 25 cm, and the median PTV volume was 1353cc (589-4213). STATA v 11 was used for all statistical analyses. Results The median cosmetic evaluation follow-up was 33.5 months. Forty women (93%) experienced an acute toxicity. The majority of these (31/40) were Grade 1 dermatitis with the remainder Grade 2 dermatitis (moist desquamation). There were no reported acute toxicities > Grade 2. Thirteen women (30.2%) were reported to have a late toxicity: Grade 1 skin in 9, Grade 1 subcutaneous tissue in 5, and Grade 2 subcutaneous in 2 of the 9 women with Grade 1 skin. There were no late toxicities > Grade 2. The acute and late toxicity rates of our main cohort and those with larger breasts were similar to those reported in the literature. On univariate analysis, there was no significant correlation (p>0.05) between toxicity and age, race, BMI, separation, tumor size, grade, or hormone receptor status, CTX regimen, and treatment position and duration. There was, however, a trend toward increased toxicity with a shorter interval between CTX completion and HRT start (p = 0.052). Conclusions The addition of adjuvant chemotherapy to the treatment regimen of breast conservation using HRT does not appear to lead to worse cosmetic outcomes. In addition, larger-breasted women, excluded from prior reports on HRT, were at no increased risk of acute or late toxicity. We found a trend toward significance suggesting that shorter intervals between CTX and HRT may be associated with increased toxicity. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-14-16.