Radiation therapy rarely causes tumor regression at a distance from the irradiated site. This phenomenon is called the abscopal effect and was first reported in 1953 [1]. Two papers on the abscopal effect have been published in this issue.

First, Biswas et al. report the case of a 65-year-old man in whom hypofractionated palliative radiotherapy for local palliation of a primary esophageal tumor resulted in regression of all primary and distant unirradiated foci without immunotherapy [2].

Next, Kono et al. report the treatment of a 58-year-old woman with lung and brain metastases following transurethral resection and Bacille Calmette–Guerin therapy for bladder cancer. The patient received local stereotactic radiotherapy to the lung in combination with an immune checkpoint inhibitor (pembrolizumab), and the brain metastasis disappeared, resulting in long-term disease-free survival [3].

The abscopal effect is thought to be caused by immune activation of the tumor [4]. Future studies are needed to characterize the genomic features of such tumors to determine in which cases this extremely rare phenomenon occurs.