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.