ASCO20: Does Adding Trastuzumab to Radiotherapy Decrease Recurrence of Breast Cancer?
Posted: Thursday, June 18, 2020
The addition of trastuzumab to radiation therapy may “modestly” reduce the recurrence of ipsilateral breast cancer or ductal carcinoma in situ in women with resected HER2-positive disease, according to the primary results of the phase III NRG Oncology/NSABP B-43 trial presented during the ASCO20 Virtual Scientific Program (Abstract 508). However, this reduction did not achieve a statistically significant improvement when compared with radiation therapy alone, according to Melody A. Cobleigh, MD, of Rush University Cancer Center, Chicago, and colleagues.
From 2008 to 2014, 2,014 patients with HER2-positive ductal carcinoma in situ resected by lumpectomy and clear margins were enrolled in the study. Patients received whole-breast radiation therapy of 25+ fractions or 16 to 17 accelerated fractions, with (n = 977) and without (n = 988) the addition of trastuzumab. A dose of 8 kg/mg of trastuzumab was intravenously administered within 1 week before treatment and 5 days after radiation therapy commenced (dose 1). In addition, 6 kg/mg of trastuzumab was intravenously administered 3 weeks after the first dose.
On primary analysis, a total of 114 ipsilateral breast tumor recurrences were reported: 63 in the radiotherapy-alone arm and 51 in the radiotherapy-plus-trastuzumab arm (hazard ratio = 0.81; P = .26). Of these recurrences, 38 were invasive, with 18 in the radiotherapy-alone arm and 20 in the radiotherapy-plus-trastuzumab arm; 76 were ductal carcinoma in situ, with 45 in the radiotherapy-alone arm and 31 in the radiotherapy-plus-trastuzumab arm.
“The addition of trastuzumab to radiotherapy did not achieve the protocol objective of 36% reduction in the ipsilateral breast tumor recurrence rate but did achieve a modest, statistically nonsignificant reduction of 19%,” the investigators concluded.
Disclosure: For full disclosures of the study authors, visit coi.asco.org.
