Chemotherapy and Metastasis to the Lungs

Lili Duda, VMD
Last Modified: November 1, 2001

Dear OncoLink "Ask the Experts,"
My 14-year-old Walker Hound has a leg tumor that was diagnosed as an undifferentiated sarcoma in June. It had already metastasized to his lungs. He's been undergoing chemo for it since then. I noticed in your FAQ that chemo isn't recommended for metastatic cancers which have spread to the lungs. What is the likelihood that continuing the chemo is a factor in retarding the lung tumor growth or limiting it's spread to other organs? Can you clarify this?  
Thank you

Lili Duda, VMD, Editor of the OncoLink Veterinary Oncology Section, responds:

There are some situations in which we do recommend chemotherapy for metastasis to the lungs and elsewhere, and also for the primary tumor. Unfortunately, as you know, when used for large primary tumors and metastasis of soft tissue sarcomas, chemotherapy is strictly palliative, and the effect usually lasts only a few months. From your description, your dog has received a thorough evaluation and rational use of chemotherapeutics to control his cancer. Palliative radiation of the leg mass is a very reasonable treatment as well.

Your question about the usefulness of continuing chemotherapy, is a difficult one. The best information any oncologist can give you is an educated guess based on clinical experience and your dog's particular medical history. It is impossible to know how slowly the metastases would grow if left alone, because the rapid growth rate following shrinkage of metastasis due to chemotherapy is a different phenomenon. As a very general rule of thumb, the growth rate slows down as tumors get larger.

I hope this information is helpful—it sounds as if you have an excellent understanding of your dog's cancer and a good oncologist to work with.