Chemotherapy in dogs is used differently than in people. In people, there are protocols that might in some cases eliminate the cancer for many years. In dogs though, the cancer usually comes back, many times in months.
(For this reason, we use a wide variety of treatments above and beyond chemotherapy in the Guide).
However, for many canine cancer cases, chemotherapy is a tool that should be considered.
When faced with a relapse and the cancer returns, veterinary oncologists will reach for a new type of chemo. Cancer cells change over time, especially when faced with chemo drugs. They become stronger. Second line drugs are selected in these cases, and these chemotherapy drugs are therefore part of “rescue protocols”.
A “rescue protocol” is used to attempt to gain a second cancer remission.
CCNU, or lomustine, is a chemotherapy drug that is used frequently for this. This exact way this drug works is not actually known precisely. But it seems to be able to interfere with the cancer cell DNA.
When lymphosarcoma returns in a dog cancer patient, CCNU may be used in the second chemo protocol. About 1 in 4 dogs responded when it was used by itself. A higher percentage of dogs achieved a second remission (the cancer went away, at least partially) when CCNU was used along with the drug DTIC.
35% of the dogs responded with this newer protocol. The effect lasted in most dogs for 83 days, although in a smaller portion of dogs the effects lasted for 25 days.
Most of the dogs had elevated liver markers. Liver injury is a very common side effect of this drug, and rarely this can be permanent. This can be lessened by supplementing with a special form of silybin, which is extracted from milk thistle (this was one reason why silybin is included in the Apocaps preparation).
CCNU is also known for immune suppression. Other side effects to watch for are GI effects vomiting, diarrhea. Rarely, mouth irritation (stomatitis), hair loss (alopecia), erosions on the eye, kidney toxicity, and lung inflammation can occur. For more information on how to support of these organs, see the Guide.
Each dog and each guardian is different. Always remember to educate yourself so you can be the best guardian you can be!
Best,
Dr D
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