title: Correlation between efficacy of PSK postoperative adjuvant immunochemotherapy for gastric cancer and expression of MHC class I.
abstract: Protein-bound polysaccharide K (PSK) is a glycoprotein that is purified from the mushroom Coriolus versicolor. In Japan, PSK is clinically used in combination with anticancer agents following gastric cancer surgery. Evaluation of the response is difficult, as efficacy is determined via antitumor immunoenhancing effects, and for that reason PSK has not become a standard therapy. The present study evaluated the expression of MHC class I in gastric cancer patients who received PSK postoperative adjuvant immunochemotherapy, and investigated the correlation between MHC class I expression and clinical outcomes. The subjects comprised 349 patients with stage II/III gastric cancer, who had received adjuvant therapy following curative resection between 1995 and 2008. MHC class I expression in the primary lesion was evaluated by immunohistochemical staining. Patients were divided into two treatment groups: one was only administered oral chemotherapy (chemotherapy-only group) and the other was administered chemotherapy plus PSK (PSK group). The clinical outcomes were compared between the two groups. The two groups did not differ in regard to their MHC class I expression. Expression-negative cases demonstrated 3-year recurrence-free survival (RFS) rates of 65% in the PSK group and 47% in the chemotherapy-only group. Therefore, the PSK group revealed a prolonged survival. For the 82 expression-negative cases with pN2 or greater, the RFS rates were 68% in the PSK group and 28% in the chemotherapy-only group, representing a significant difference. Thus, PSK adjuvant immunochemotherapy may be effective in MHC class I-negative patients, who are in a state of antitumor immunological tolerance, and patients with advanced lymph node metastasis of pN2 or greater.
authors.affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Abeno-Ku, Osaka 545-8585,  Japan.
authors.forename: Gentaro
authors.initials: G
authors.lastname: Ito
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tanaka
authors.forename: Masaichi
authors.initials: M
authors.lastname: Ohira
authors.forename: Mami
authors.initials: M
authors.lastname: Yoshii
authors.forename: Kazuya
authors.initials: K
authors.lastname: Muguruma
authors.forename: Naoshi
authors.initials: N
authors.lastname: Kubo
authors.forename: Masakazu
authors.initials: M
authors.lastname: Yashiro
authors.forename: Nobuya
authors.initials: N
authors.lastname: Yamada
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Maeda
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Sawada
authors.forename: Kosei
authors.initials: K
authors.lastname: Hirakawa