A short course of immunotherapy before surgery may offer remarkably durable protection for some patients with stage two or three bowel cancer. In the NEOPRISM-CRC trial, 32 patients with a specific genetic form of bowel cancer received pembrolizumab for up to nine weeks before surgery instead of the usual post-surgery chemotherapy. After nearly three years of follow-up, none of the patients had experienced a cancer recurrence, including those who still had small traces of disease after treatment.