Abstract 2687: Immunopotentiator, protein-bound polysaccharide K, is efficient for advanced gastric cancer with negative expression of MHC Class I

Abstract It has been reported that down-regulation of MHC class I in cancer cells was associated with poor prognosis of gastrointestinal cancer, because of immunological escape from the attack of antigen specific cytotoxic T lymphocytes. Protein-bound polysaccharide K (PSK), nonspecific immunopotentiator, is approved for adjuvant chemotherapy against Stage II/III gastric cancer in Japan. Several randomized studies have demonstrated the efficacy of immunochemotherapy using PSK for colon and gastric cancer. The aim of this study was to investigate whether expression of MHC class I was associated with prognosis of the patients who received PSK as postoperative adjuvant therapy. We retrospectively analyzed total of 349 gastric cancer patients who underwent curative gastric cancer surgery in Department of Surgical Oncology, Osaka City University from 1995 to 2008. We investigated the expression of MHC class I antigen in primary lesions using immunohistchemistry to compare the relapse-free survival (RFS) between the patients receiving only oral fluoropyrimidine agents (the control group) and plus PSK (the PSK group). 124 patients were assigned to the PSK group and 225 patients to the control group. There were no differences between two groups in background factors. In analysis of MHC class I expression, 193 patients were classified as MHC class I positive, and 156 patients as MHC class I negative. RFS was significantly better in MHC class I positive group. Combination of anti cancer agents with PSK did not improve the RFS among total patients. However, in patients with multiple lymph node metastasis and negative expression of MHC class I, the 5-year RFS of the PSK group was significantly better than the control group. These results suggested that the expression of MHC Class I in primary lesion could be one of the prognostic markers related to the efficiency of adjuvant immunochemotherapy for patients with gastric cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2687. doi:10.1158/1538-7445.AM2011-2687