Usefulness of polysaccharide K (PSK) as postoperative adjuvant immunotherapy in patients with stage IV gastric cancer

Background. We investigated retrospectively the usefulness of polysaccharide K (PSK) administration for prolonging survival after noncurative resection in patients with stage IV gastric cancer who underwent surgery at our department. Methods. 357 patients with gastric cancer evaluated as stage IV according to thegeneral rules for gastric cancer study, 11th edn (1985) of the Japanese Research Society for Gastric Cancer, who were expected to succumb to surgical death or postoperative death within 2 months were studied. The patients were divided into two groups: total PSK dosage greater than or less than 180g. Survival rates were calculated for each group. Results. In these stage-IV gastric cancer patients, the 5-year and 10-year survival rates in the PSK group were both 13.9%. In the non-PSK group, the rates were 8.7% and 7.0%, respectively. The survival rates were significantly higher in the PSK group (p = 0.0001). The survival rate was also calculated with respect to the staging factors. Patients in the PSK group who had H0, P0, se or milder and n3 or n4 showed a significantly higher survival rate than those with these staging factors in the non-PSK group (p = 0.010). Conclusion. PSK administration prolonged survival in stage-IV gastric cancer patients, the effect being marked in patients with severe lymph node metastasis. We suggest that be administered as adjuvant therapy in stage-IV gastric cancer patients with severe lymph node metastasis (n3, n4).