P-115 PEMREC: A phase II study to evaluate safety and efficacy of neo-adjuvant pembrolizumab and radiotherapy in localized microsatellite stable rectal cancer

Abstract

Locally advanced rectal cancer remains a clinical challenge with few improvements noted over the past few decades. Although immunotherapy has no current clinical role in microsatellite stable (MSS) colorectal cancer, preclinical models suggest that radiotherapy (RT) can enhance neoantigen presentation, modulate the microenvironment, and improve the likelihood of anti-tumor activity with checkpoint inhibitor use. This prospective phase II trial will test that hypothesis in addition to confirming the safety of this approach using a “window-of-opportunity” study design with the anti-PD-1 agent pembrolizumab.