Chemoimmunotherapy as long-term maintenance therapy for cancer.

Homeostatic immune regulatory mechanisms can mediate premature termination of therapy-induced antitumor T-effector cell responses. Administration of cyclophosphamide (CY) prior to intratumoral IL-12 and GM-CSF delivery blocked post-treatment T-suppressor cell rebound via elimination of the pre-existing T-suppressor cell pool, allowed repeated activation of antitumor cytotoxic T-cells and resulted in the cure of advanced spontaneous tumors.