Practical Matters: Consider chemotherapy in these cases, but set your goal first

Localized primary tumors with a minimal risk for metastasis are commonly treated with surgery or radiation. But chemotherapy may occasionally be used to treat these tumors instead of or in addition to standard local therapy. And systemic chemotherapy is indicated after local treatment in tumors that are commonly widespread or demonstrate a high rate of metastatic behavior (e.g. osteosarcoma, oral melanoma). Understanding cell growth, tumor biologic behavior, and metastatic patterns of specific tumor types is essential before formulating treatment plans. Reviewing drug mechanisms of action and associated toxicoses is vital as well.

But before you use chemotherapy in any patient with a tumor, you and the owner must decide whether the goal is a cure or palliation. A cure is ideal, but it is unrealistic in most cases unless it was the goal from the beginning. If a cure is intended, aggressive therapy may provide substantial long-term benefits, and a relatively high level of short-term toxicosis may be justified.

More commonly, the accepted goal of cancer therapy in veterinary medicine is palliation—remission and a prolonged disease-free interval. In such cases, chemotherapy toxicosis is minimized in an attempt to prolong an acceptable quality of life.

Kevin A. Hahn, DVM, PhD, DACVIM (oncology)

Gulf Coast Veterinary Specialists

1111 W. Loop South, Suite 150

Houston, TX 77027