Acute Toxicity Associated With A 3-Week Versus A Standard 5week Regimen For Locoregional Breast Radiotherapy Delivered In The Unicancer Hypog-01 Phase Iii Trial

In most countries, the 5-week normofractionated (NF) locoregional radiotherapy (RT) is still the standard of care for breast cancer with an indication for regional lymph node irradiation. HypoG-01 (NCT03127995) is a randomized phase 3 clinical trial evaluating the safety and efficacy of a 3-week moderate hypofractionated (HF)-RT against NF-RT regimen. Here, we report for the first time the acute toxicity results, a secondary endpoint of the trial. Women with pT1-3 pN0-3 M0 breast cancer were randomized 1:1 after surgery to receive either HF-RT: 40 Gy/15 fractions/3 weeks or NF-RT: 50 Gy/25 fractions/5 weeks. Acute toxicities were graded using CTCAE V4.0 at baseline, weekly during RT, and 1 month after the end of RT (end of treatment visit); the maximum grading is reported. Since arm lymphedema is the primary endpoint of the trial, it is not included in the acute toxicities of interest. From 09/2016 to 03/2020, 29 French sites enrolled 1265 women (HF-RT arm: 633, NF-RT arm: 632). All patients (median age: 58 years) received their allocated RT and completed their scheduled end of treatment visit. Acute grade 3 toxicities were rare in both treatment arms (HF-RT: 5.4%, NF-RT: 5.7%) and no grade 4-5 toxicities were observed (Table). The rate of overall grade 2 or higher acute toxicities was lower with HF-RT (38.4%) than with NF-RT (48.1%). Grade 2 or higher dermatitis were more frequent in patients with BMI ≥30 in both arms: 34/118 (29%) in HF-RT and 59/124 (48%) in NF-RT. In total 18 patients experienced at least 1 acute Serious Adverse Event (HF-RT: 10, NF-RT: 8) of which only 2 were considered treatment-related (HF-RT: 1, NF-RT: 1).Table: 121MOAcute adverse events of interestHF-RTNF-RTTOTALG 1 n (%)G 2 n (%)G 3 n (%)HF Total n (%)G 1 n (%)G 2 n (%)G 3 n (%)NF Total n (%)n (%)Dermatitis418 (66)82 (13)9 (1)509 (80)365 (58)183 (29)13 (2)561 (89)1070 (85)Fatigue263 (42)41 (6)4 (1)308 (49)293 (46)45 (7)4 (1)342 (54)650 (51)Pain223 (35)39 (6)4 (1)266 (42)246 (39)46 (7)3 (0)295 (47)561 (44)Dysphagia109 (17)16 (3)-125 (20)135 (21)11 (2)-146 (23)271 (21)Pruritus112 (18)10 (2)-122 (19)155 (25)10 (2)3 (0)168 (27)290 (23)Dyspigmentation74 (12)4 (1)-78 (12)69 (11)11 (2)2 (0)82 (13)160 (13)Respiratory disorders88 (14)11 (2)1 (0)100 (16)125 (20)11 (2)2 (0)138 (22)238 (19)Cardiac disorders3 (0)2 (0)1 (0)6 (1)1 (0)-1 (0)2 (0)8 (1) Open table in a new tab In women receiving locoregional RT, acute toxicities with a 3-week moderately hypofractionated regimen were mild and raised no important acute safety concerns. Further long-term follow-up is ongoing.