Breast Cancer

PV 01 - Poster Viewing Q&A - Session 1

SU_4_2032 - APBI (Accelerated Partial Breast Irradiation) Versus WBI (Whole Breast Irradiation) Delivered with the Same Dose Fractionation: A Propensity Score Matched Analysis of Two Prospective Studied Cohorts

Sunday, September 15
1:15 PM - 2:30 PM
Location: ASTRO Innovation Hub

APBI (Accelerated Partial Breast Irradiation) Versus WBI (Whole Breast Irradiation) Delivered with the Same Dose Fractionation: A Propensity Score Matched Analysis of Two Prospective Studied Cohorts
Z. Abou Yehia, A. Gupta, D. Toppmeyer, N. Ohri, F. Eladoumikdachi, and B. G. Haffty Jr; Rutgers Cancer Institute of New Jersey, New Brunswick, NJ

Purpose/Objective(s): The recent updates of the RAPID and RTOG 0413 trials have led to renewed interest in the question of APBI versus WBI outcomes. On the other hand, IMPORT-LOW, which was the only APBI randomized study strictly testing treatment volume without the confounding effect of dose-time factors, reported non-inferiority of APBI with fewer late toxicities. In this study, we report our institutional experience comparing two matched prospective cohorts of breast cancer patients treated with the same dose-fractionation using APBI or WBI.

Materials/Methods: Two phase II trials using the same dose fractionation of 4995 cGy in 15 fractions enrolled early stage breast cancer patients at our institution between 2008 and 2017; one utilizing APBI and the other utilizing WBI. A total of 184 patients were enrolled in both trials (34 on the APBI and 150 on the WBI). Patients who received regional nodal irradiation or who were treated prone on the WBI trial were excluded. We then performed a propensity score 1:1 match between the two cohorts using age, histology, breast volume and seroma volume. Outcomes of interest included loco-regional control, acute and late toxicity and cosmesis. Cosmesis was scored using the Harvard Cosmesis Scale; toxicities were recorded using CTCAE version 4.03.

Results: A total of 68 patients were matched. All patients had T1-T2, N0 disease with negative margins. Median follow up was 62.5 months [6-96] for the WBI patients versus 92.5 months [23-119] for the APBI patients. Median time to final cosmetic evaluation was 24.5 months [6-67] in the WBI cohort versus 90 months [9-119] in the APBI cohort. In accordance with the propensity score match, breast size mean (1400 cc vs 1600 cc; p =0.15), seroma size mean (37 cc vs 49 cc, p=0.27) and mean age (58 vs 60, p=0.17) were similar in the two groups. Ipsilateral breast recurrence rates were similar between the two groups (2/34, 5.9%) in the APBI versus (3/34, 8.8%) in the WBI, p= 1.0. In the WBI group, 1 patient had distant metastasis 6 years after treatment and 1 patient had a contralateral breast recurrence (CBR). In the APBI group, 4 patients had CBR. At final cosmetic evaluation, 91.2% in each cohort had excellent/good cosmesis, 5.9% in each cohort had fair cosmesis and 2.9% (1 patient in each cohort) had poor cosmesis, p = 0.92. In the WBI cohort, 11/34 patients had grade 2 or 3 acute toxicities (32.4%) versus 2/34 in the APBI group (5.9%), p= 0.01. In the WBI cohort, 12/34 patients had grade 2 or 3 late toxicities (35.3%) versus 7 in the APBI group (20.6%), p= 0.28.

Conclusion: Clinical outcomes, toxicity profiles and cosmetic results were similar in patients treated with APBI or WBI, with significantly fewer grade 2–3 acute side effects after APBI. Our results are in agreement with the IMPORT-LOW outcomes and suggest that with similar fractionation schemes APBI and whole breast are associated with similar outcomes.

Author Disclosure: Z. Abou Yehia: None. A. Gupta: None. D. Toppmeyer: None. N. Ohri: None. F. Eladoumikdachi: None. B.G. Haffty: Research Grant; Breast Cancer Research Foundation. Board of Directors-Science Liaison; RSNA.

Zeinab Abou Yehia, MD

Rutgers Robertwood Johnson Medical School

Biography:
My name is Zeinab Abou Yehia; I graduated from the American University of Beirut in Lebanon. Recognizing the importance of research in the growth of the radiation oncology field, I enrolled in the Scholars in HeAlth Research Program (SHARP), a 12 credit program that was funded by the NIH to provide the required foundation for health scholars to pursue a career in clinical research. I then worked as a research fellow and a sub-investigator in two international oncology clinical trials at AUB. I then endorsed the opportunity to work as a post-doctoral research fellow clinical research fellow in the radiation oncology department at the University of Texas MD Anderson Cancer Center. I completed my intern year at the University of Oklahoma and I am now a PGYIII in radiation oncology at Rutgers. I envision myself in a future of academic medicine where I am able to combine my compassion to patients with my enthusiasm to make a difference on a larger, population-based scale through advancing clinical knowledge in research.

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SU_4_2032 - APBI (Accelerated Partial Breast Irradiation) Versus WBI (Whole Breast Irradiation) Delivered with the Same Dose Fractionation: A Propensity Score Matched Analysis of Two Prospective Studied Cohorts



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