The Effects of CCNU on Dogs
Dear OncoLink "Ask the Experts,"
I would like to get information about an oral chemotherapy drug called "CCNU". I would like to know the pros and cons before giving it to my 10 year old Boxer. She has been diagnosed with a mast cell tumor on the lower part of her hind leg, near the foot. Any information you give me would be greatly appreciated.
Lili Duda, VMD, Editor of the OncoLink Veterinary Oncology Section, responds:
In general, chemotherapy is used in mast cell tumors under two general circumstances. First it is used when the primary tumor is treated "definitively" with surgery with or without radiation therapy, but there are some concerns that there may be metastasis (or spread of the tumor) beyond the site of the primary tumor. Second, chemotherapy can be used to treat a large tumor that is untreatable by surgery and/or radiation, or for tumors that have spread elsewhere in the body.
There is no single or combination chemotherapy protocol that has a high efficacy against mast cell tumors once they have become very large or have spread. Also, we do not know what the best chemotherapy options is/are to manage potentially small amounts of tumor that MIGHT have spread. Traditionally, most oncologists have relied on prednisone (cortisone) either as a solitary drug or combined with other drugs. Every oncologist has their own preferred protocol (for example, one combination protocol uses two chemotherapy drugs—vinblastine and cyclophosphamide—along with prednisone). However, no large studies have been done to date.
CCNU (Lomustine) is not a new drug. It has been used in both dogs and humans for quite a while in a variety of tumors. What is relatively new is its use in mast cell tumors. There are some prelimary results that suggest that CCNU might be of some use in mast cell tumors. One of the appeals of CCNU is that it is given orally so that trips to the veterinarian can be minimized. However, it is important to monitor blood cell counts and to contact your veterinarian immediately if your pet has side effects such as vomiting, lethargy, or loss of appetite.