IMPORT LOW: in response to Vaidya et al13 Mar 2018
We reject the inference of a “survival benefit” for patients receiving partial breast irradiation (PBI) within the IMPORT LOW trial and caution against any such interpretation when the number of events reported is so small1. There is no suggestion of a difference in disease-free and overall survival across IMPORT LOW treatment groups. The TARGIT trialist’s claim of survival benefit in their own trial relates to non-breast cancer deaths and the data cited are from a selected subset of patients. In IMPORT LOW, there were 9 cardiac deaths occurring 6-36 months following randomisation, 4 after left- and 5 after right-sided breast cancer, so no suggestion of an early radiation induced effect. Lung cancer laterality in relation to the treated breast was similar for ipsilateral and contralateral tumours, with 18/19 cases developing within 5 years of randomisation. These data fail to support an increase in radiation-induced second cancers after whole breast irradiation (WBI). Therefore, the TARGIT trialist’s suggestion that WBI causes inferior survival at 5-years’ follow-up due to either cause appears unsubstantiated.