THE ROLE OF LYMPHOCYTES AND HISTIOCYTES AS MECHANISM OF ACTION OF BCG FOR BLADDER CANCER

Antitumor activity of BCG for transitional cell carcinoma of the urinary bladder was evaluated in 103 patients from October, 1983 to October, 1989 at Hirosaki University Hospital. At the same time, the role of various inflammatory cells infiltrating in the bladder wall after intravesical BCG instillation as mechanism of action of BCG was studied. Of 72 patients with superficial bladder cancer, 19 showed a complete response and 28 showed a partial response. The effective rate was 65.3 percent. Significant efficacy was obtained in patients received more than 5 times instillation of BCG. Before intravesical BCG instillation, a small number of lymphocytes or plasma cells infiltrated in the stroma of the tumor. But histiocytes, neutrophils or eosinophils were hardly found. After BCG instillation, the degree of infiltration of each of them tended to increase. The mean degree of infiltration of those inflammatory cells almost all significantly increased in the stroma of the tumor, while only lymphocyte and histiocyte counts significantly increased in both the basal areas of the advancing margin of tumor cells and the tumor free submucosa after BCG instillation. Epithelioid granulomas were recognized almost in the basal areas of the advancing margin of tumor cells and the tumor free submucosa after BCG therapy. Langhans' giant cells were occasionally found within these lesions. In 2 patients marked central necrosis (caseation) was noticed in epithelioid granulomas. In BCG effective cases with superficial bladder cancer lymphocytes and histiocytes increased significantly in all of the stroma of the tumor, the basal areas of the advancing margin of tumor cells and the tumor free submucosa. On the other hand, in BCG noneffective cases they increased significantly only in the stroma of the tumor. Subsets of lymphocytes which increased after intravesical BCG instillation were mainly T pan cells with the predominance of T helper/inducer cells (Th/Ts ratio always>1).