Dacarbazine in Dogs With Lymphoma

Lymphoma is a cancer of the T- and B-cells of the lymphatic system, and the most common cancer among dogs. Because of its prevalence, it has one of the highest remission rates of any canine cancer, but these remissions almost never last more than a year, after which point future remissions become extremely unlikely and short-lived. The use of dacarbazine in dogs with lymphoma is typically as a rescue agent following one of these relapses.

Overview

Dacarbazine is a chemotherapeutic agent that operates by interfering with the formation and growth of rapidly-dividing cancer cells. It is almost always a second line protocol for use when the initial chemotherapy has failed to halt the spread of the cancer. In dogs with lymphoma, dacarbazine is usually prescribed alongside other chemotherapy drugs like doxorubicin and dactinomycin.

Administration

The drug is administered as an IV drip, and can be given in many small doses or fewer large ones. In the former case, the drip is administered once a day for five consecutive days. The latter example would have the drug pushed over a two to eight hour period, and would required additional treatments after three weeks. As an intravenous drug, dacarbazine’s success is highly dependent on proper placement of the IV, and in most cases requires the assistance of a veterinary professional.

Side Effects

As with most chemotherapy drugs for dogs, dacarbazine is very well tolerated in comparison to humans. Even among chemo drugs for dogs, dacarbazine still has a lower rate of negative side effects. Nevertheless, nausea and vomiting are common, with almost 50 percent of dogs vomiting during administration. The area around the IV needle may end up bruised and tender as a result of the necessary repeated injections.

Clinical Effectiveness

Dacarbazine is designed as a repeated treatment and is not usually effective after the first visit. When combined with a drug like doxorubicin, which has a more immediate effect, the efficacy of dacarbazine is increased. Furthermore, it seems to somewhat negate the cancer’s ability to adapt to doxorubicin. According to one study, out of 15 dogs, five responded to the first round of treatment, and three more responded to the second.

Other Considerations

Because of its method of action, dacarbazine can easily corrode tissues it comes into contact with. The needle must therefore be handled very gently and the injection site checked at each administration to ensure no lasting tissue damage.

Conclusion

Dacarbazine is an effective rescue protocol option for dogs with lymphoma because it is well-tolerate, and results in an extension of the (usually quite short) second remission.