Long‐term follow‐up of patients with resected pancreatic cancer following vaccination against mutant K‐ras

Abstract K‐ras mutations are frequently found in adenocarcinomas of the pancreas and can elicit mutation‐specific immune responses. Targeting the immune system against mutant Ras may thus influence the clinical course of the disease. Twenty‐three patients who were vaccinated after surgical resection for pancreatic adenocarcinoma (22 pancreaticoduodenectomies, one distal resection), in two previous Phase I/II clinical trials, were followed for more than 10 years with respect to long‐term immunological T‐cell reactivity and survival. The vaccine was composed of long synthetic mutant ras peptides designed mainly to elicit T‐helper responses. Seventeen of 20 evaluable patients (85%) responded immunologically to the vaccine. Median survival for all patients was 27.5 months and 28 months for immune responders. The 5‐year survival was 22% and 29%, respectively. Strikingly, 10‐year survival was 20% (four patients out of 20 evaluable) versus zero (0/87) in a cohort of nonvaccinated patient treated in the same period. Three patients mounted a memory response up to 9 years after vaccination. The present observation of long‐term immune response together with 10‐year survival following surgical resection indicates that K‐ras vaccination may consolidate the effect of surgery and represent an adjuvant treatment option for the future.