Abstract P3-12-13: Comparison of accelerated partial breast irradiation (APBI) with whole breast irradiation (WBI) using 3D conformal external beam radiation therapy (3D CRT)

Abstract

Abstract Purpose: To compare accelerated partial breast irradiation with whole breast irradiation in post breast conservation surgery (BCS) women with breast cancer. Material and methods: Women >35 years of age with invasive or noninvasive breast cancer ≤4 cm treated by BCS were randomized to 3D CRT APBI (34 Gy in 10 fractions given twice daily) or WBI (40 Gy in 16 fractions given once daily ± boost irradiation).The primary outcome was ipsilateral breast tumour recurrence and important secondary outcomes were adverse cosmetic outcome (fair or poor on a HARVARD/NSABP/RTOG breast cosmesis grading scale) and toxicity using the RTOG scores and LENT SOMA scale. Radiation toxicities and cosmesis was assessed directly by radiation oncologist during radiotherapy and in follow up.Patient and tumour characteristics, locoregional recurrence and distant metastases rates were compared using Fisher's exact tests.All statistical tests were two sided p values less than 0.05 were considered statistically significant. Results: Between June 2011 and December 2015, 133 women were randomized to 3D CRT APBI or WBI. Patient characteristics were balanced between two arms. There was an increased rate of acute grade 2 dermatitis in WBI arm(p=0.33). Median follow up was 60 months(range 9-84 months). Grades 1 and 2 late radiation toxicities were higher in the WBI arm compared to the APBI arm; pigmentation, fibrosis and breast shrinkage were significantly more in the WBI arm. Grades 3 and 4 late toxicity was not seen in any of the treatment arms. Adverse cosmesis at last follow up was significantly higher in patients treated with WBI, 32% as compared to 6% with APBI (p=<0.001). Local recurrence with APBI was 3% as compared to 1.5% with WBI and distant metastasis rate was high in WBI arm as compared with APBI, 5.9% vs 3% respectively; both not statisticaly significant. Table 1.Patient and tumor characteristicsCharacteristicsAPBI(n=65)WBI(n=68)p-valueMean age(range)50(36-75)(36-75)50(37-67)(37-67)0.13T- Stage T134(52)37(54) T228(43)28(41)0.96T33(5)3(4) N stage N057(88)59(87) N17(11)28(41)1.00N21(1)1(1) Grade 114(22)12(18) 237(56)40(59)0.5314(22)16(23) Surgical margins Negative60(92)61(90)0.79Positive5(8)7(10) LVI No56(86)55(81)0.49Yes9(14)13(19) ER Positive42(65)45(66) Negative19(29)21(31)1.00Unknown5(6)2(3) PR Positive38(58)39(57) Negative23(35)25(37)1.0Unknown4(7)4(6) Her2-neu Positive7(11)6(9)0.78Chemotherapy Yes35(54)52(76)0.78No30(46)16(24) Hormone therapy Yes49(75)49(72)0.78No16(25)19(28) Trastuzumab Yes3(43)3(50)1.00No4(57)3(50) Conclusion: In women with BCS, APBI was associated with better cosmetic outcome and late radiation toxicities compared to WBI. Local recurrence and distant metastasis was comparable in both the arms. Citation Format: Yadav BS, L S, Sharma SC, Singh R, Dahiya D. Comparison of accelerated partial breast irradiation (APBI) with whole breast irradiation (WBI) using 3D conformal external beam radiation therapy (3D CRT) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-12-13.