Significant clinical response of advanced colon cancer to peptide vaccine therapy: a case report

Partial response (PR) was obtained in a patient with advanced colon cancer following peptide vaccine therapy. A 61-year-old woman was referred to our hospital for peptide vaccine therapy. She had undergone sigmoidectomy at a nearby hospital and eventually developed multiple metastases to the lung and pelvic lymph nodes with left hydronephrosis. A ureteral stenting catheter had been inserted for left hydronephrosis, and oral opioids had been administered for relief of pain in the left pelvic region. Three tumor-antigen-derived peptides (RNF43, TOMM34, and KOC1) and two human VEGFR-derived peptides (VEGFR1 and VEGFR2) were used as a cocktail. The peptide cocktail was subcutaneously inoculated on days 1, 8, 15, and 22 and repeated at 14-day intervals. The patient's serum level of carcinoembryonic antigen was 28.9 ng/mL (N<5 ng/mL) before treatment, and it decreased promptly after the initiation of therapy to within a normal range. Evaluation of computed tomography images at week 5 revealed PR as determined by the Response Evaluation Criteria in Solid Tumor criteria. After month 3, the oral opioid was discontinued. The PR lasted for 4 months and was followed by stable disease for another 4 months. No particular adverse effects were observed. A cytotoxic T lymphocyte (CTL) response was evaluated by immunosorbent spot assay, and a positive CTL response was recognized against at least one of five peptides at each end of the six courses. Immunotherapy has been proven to slow tumor growth by inducing an active antitumor immune response; and therefore, significant tumor shrinkage is rarely observed. To our knowledge, this is the first case report of PR presented in a patient with advanced colon cancer.