Outcomes in DCIS Patients Treated with Hypofractionated Whole Breast Radiation Therapy with Integrated Boost Compared to Standard Fractionation with Concomitant Boost

Abstract

Hypofractionation for ductal carcinoma in situ (DCIS) is not yet formally recommended by national guidelines. We compared outcomes after hypofractionated radiation therapy (HRT) with an integrated boost to conventional fractionation (CRT) with sequential boost for DCIS. We queried our institutional database for DCIS patients treated with whole breast RT after lumpectomy between Jan 2004 and Nov 2015 and followed for greater than 2 years. HRT delivered 2.25 Gy per fraction (fx) to 45 Gy to the whole breast with an integrated 2.8 Gy tumor bed boost per fx for a total of 56 Gy in 20 fx over 4 weeks. CRT delivered 50 Gy in 2 Gy fx to the whole breast plus a sequential 10-16 Gy tumor bed boost. Treatment fields utilized field-in-field tangential design or IMRT. CRT patients were propensity score matched to HRT patients in a 2:1 ratio using age, bra cup size, DCIS grade, histologic subtype (comedo vs non-comedo) and use of endocrine therapy. Toxicity was graded using CTCAE v3 and stratified as early (<6 weeks from RT completion) vs late. Acute toxicity was reported weekly during radiation. Physician reported cosmesis was scored using the Harvard scale (1 excellent, 2 good, 3 fair, 4 poor). Kaplan Meier estimates for ipsilateral invasive/DCIS recurrence at 5 years were calculated. Univariate logistic regression to predict toxicity outcomes employed generalized estimating equations to control for the within subject correlation. Forty-six patients undergoing HRT were eligible and were matched to 92 CRT patients. Median follow-up of all patients was 76 months (range 24-164). Median age was 59 years (40-91). Cup size was B or smaller in 31%. Comedo and grade 3 histology were present in 28% and 46%, respectively. Endocrine therapy was taken by 55%. Final margin status was close or positive in 12% and 2% of patients, respectively. There were no statistically significant differences in any demographic, clinical or treatment characteristics following matching. Recurrence free survival after CRT and HRT was 93.7% and 97.8% at 5 years (p=0.74), respectively. In patients who had cosmesis reported (61% available), median final score was 1.27 for CRT and 1.25 for HRT (chi square p=0.96).Abstract TU_4_3355; Table 1VariableHRT%CRT%Odds RatioP-valueCIAcute skin color change19%38%0.400.030.17-0.93All acute toxicity ≥ Grade 222%52%0.25<0.010.12-0.55Acute tissue complications ≥ Grade 22%26%0.06<0.010.01-0.51All late toxicity ≥ Grade 22%5%0.390.300.06-2.32Late tissue complications ≥ Grade 22%4%0.490.420.09-2.77 Open table in a new tab In this single institution experience, DCIS patients treated with HRT with concurrent boost experienced similar or improved toxicity compared to CRT matched controls. Rates of recurrence were similar between CRT and HRT groups. HRT toxicity data and rate of recurrence was consistent with other investigations utilizing HRT and boost.