Neoadjuvant immunotherapy with interferon of the spontaneously metastasizing murine B16F10L melanoma

We have previously demonstrated that administration of interferon a/b (IFN) for 4–5 days after challenge with a transplantable Moloney sarcoma virus‐induced tumor completely inhibited tumor development. In the present study, we examined the therapeutic effects of IFN on mortality induced by metastatic dissemination of the B16F10L murine melanoma. IFN was administered at various times in relation to the surgical removal of primary tumor: days ‐5 to ‐1 prior to tumor excision (neo‐adjuvant protocol), or for 5 days after tumor excision, beginning on days 1, 6 or 11 after excision of the primary tumor (adjuvant protocols). The neo‐adjuvant protocol was superior to all other protocols, significantly increasing percentage survival (56% vs. 0%) and median survival time (>84 days vs. 33 days) compared to untreated controls, as well as to all adjuvant protocols. In contrast, IFN treatment on days 1 to 5 after excision of the primary tumor decreased median survival time of cases compared to untreated controls (20 days vs. 33 days). Both IFN‐induced inhibition and enhancement of metastatic dissemination were dose‐dependent, with higher amounts of IFN producing greater inhibition or enhancement. The superior therapeutic efficacy of the neo‐adjuvant IFN treatment was associated with increased spleen and lung‐derived natural killer cell cytolytic activity (on days ‐4, 0 and 2) followed by a later (day 13) increase in lung‐associated cytolytic T‐cell responses.