Effect of radiation therapy for urologic cancer on circulating thymus derived lymphocytes

Studies of T rosette forming lymphocytes, mediators of cellular (tumor inhibiting) immunity, in 50 patients with a variety of urologic tumors, of whom 18 were irradiated and 32 were not, revealed that local radiation therapy for urologic cancer produces more than a 50% reduction in the number of circulating lymphocytes and more than a 68% reduction of the T lymphocyte moiety which persists for up to 2 yr. Results suggest that the systemic immunosuppressive consequences of adjunctive radiation therapy may increase the prospects of implantation and clonal outgrowth of circulating tumor cells. The indications for adjunctive radiation therapy for urologic cancer should be evaluated in the light of these findings.