Modeling tumor regrowth and immunotherapy

Deterministic models describing mechanisms underlying tumor growth. suppres sion. and regrowth are proposed and fit to kinetic data on B cell lymphoma in mice. It is demonstrated that either a modest change in the effectivenes s of killer cell suppression, or the existence of a variant nonimmunogenic clone of tile tumor cells, call explain tile regrowth of a tumor after init ial suppression. Adjuvant immunotherapy after establishing tile cancer dorm ancy is modeled as a stimulated increase of tile how of killer cells into t he tumor or a local increase of the rate of proliferation of these cells il l a, tumor. We modeled the immunotherapy consisting of impulse injections o f immune lymphocytes in tile vicinity of the tumor. Our numerical experimen ts show that this immunotherapy does not completely destroy the tumor. alth ough thereafter the tumor may persist in a dormant cancer state ol have its regrowth markedly delayed. (C) 2001 Elsevier Science Ltd. All rights reser ved.