Plasma ultrafiltration as cancer therapy

Studies of cancer-related immunosuppression reveal the presence of low-molecular-weight (less than 10 kilodaltons) serum factors capable of in vitro lymphocyte suppression. Removal of suppressor factors by ultrafiltration (UF) prolongs survival in tumor-bearing rabbits. This study determined the prevalence of low-molecular-weight suppressor factors in patients with cancer and normal volunteers and evaluated safety and feasibility of UF in patients with cancer. Intact serum and serum ultrafiltrate from 32 patients with cancer and 24 normal volunteers was examined with mitogen-induced lymphocyte blastogenesis. Eleven (34%) of serum samples from patients with cancer suppressed blastogenesis, while ultrafiltrate was suppressive in 25 (78%). None of the ultrafiltrate from normal volunteers was suppressive. Six patients with cancer underwent UF in a phase I trial, completing 82 sessions. There were no therapy-related complications, and high-performance liquid chromatography showed significant (greater than 90%) posttreatment reduction in serum suppressor factors.