Effectiveness of immunochemotherapy with PSK, a protein-bound polysaccharide, in colorectal cancer and changes of tumor marker.

In the present study, curatively resected patients of colorectal cancer at pTNM stages II and III were selected. Patients receiving postoperative combined PSK, a protein-bound polysaccharide, and fluoropyrimidine therapy (PSK + chemotherapy group) were compared with patients receiving postoperative chemotherapy alone (chemotherapy group) during the same period of study. Three-year disease-free survival rates were evaluated and the postoperative changes of serum type IV collagen level were investigated. The results confirmed a significant improvement of the three-year disease-free survival rate in the PSK + chemotherapy group compared to the chemotherapy group, suggesting that PSK is useful as postoperative prognosis control including relapse prevention for colorectal cancers at pTNM stage II and III. Analysis of the postoperative changes of serum type IV collagen level showed significantly higher levels in the chemotherapy group than in the PSK + chemotherapy group, and this tendency was sustained for 12 months after surgery. This observation is speculated to be caused by inhibition of vascular basement membrane destruction by PSK, leading to inhibition of release of type IV collagen into the blood. These results indicated a possibility that combined PSK and chemotherapy inhibited metastasis, thereby reducing the risk of relapse and leading to improvement of the three-year disease-free survival rate.