Influence of the administration schedule on the therapeutic effect of interleukin-2.

The local and systemic therapeutic effects of multiple peritumoral injections of recombinant human interleukin-2 (IL-2) were tested against the syngeneic, immunogenic mammary carcinoma MC2 implanted subcutaneously into C3H/He mice. Multiple (12) low-dose injections had a greater local therapeutic effect than the same total amount of IL-2 given in 2 injections. Peri-tumoral injections were equally effective in inhibiting the growth of the injected tumors in normal and in immunized mice. The systemic therapeutic effect was manifested by the inhibition of tumors implanted contra-laterally to the injected tumors, and was only discernible in non-immunized mice.