Radiation therapy enhances immunotherapy response in MSS colorectal and pancreatic adenocarcinoma

Overcoming intrinsic resistance to immune checkpoint blockade for microsatellite stable (MSS) colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC) remains challenging. A phase I study at Harvard Medical School (Boston, MA) evaluated the combination of radiation, ipilimumab and nivolumab for MSS mCRC and mPDAC. Disease control rate by intention to treat was 25% for CRC (95% CI 13-41; ten of 40 patients) and 20% for PDAC (7-41; five of 25 patients). DCR in per-protocol analysis, defined as receipt of radiation, was 37% for CRC (95% CI 19-58; ten of 27 patients) and 29% for PDAC (10-56; five of 17 patients). The authors conclude that the study provided proof of concept of combining radiation with immune checkpoint blockade in immunotherapy-resistant cancers.