Temozolomide alone or in combination with doxorubicin as a rescue agent in 37 cases of canine multicentric lymphoma

Temozolomide (TMZ) is an alkylating agent previously used in conjunction with doxorubicin (DOX) to treat dogs with relapsed lymphoma. However, there are very limited data for this drug when used as single agent. The aim of this retrospective study was to evaluate the efficacy and toxicity of TMZ in dogs with relapsed multicentric lymphoma that failed multi‐agent chemotherapy protocols, and compare the outcome to a group of dogs receiving the same drug in combination with DOX. Twenty‐six patients were included in the TMZ group and 11 in the TMZ/DOX group. Responses were evaluated via retrospective review of the medical records. The overall median survival time (MST) for both groups was 40 days (range 1‐527 days). For the TMZ group, median time to progression (TTP) was 15 days (range 1‐202 days) and MST 40 days (range 1‐527 days), with an overall response rate (ORR) of 32% and 46% recorded toxicities. For the TMZ/DOX group, median TTP was 19 days (range 2‐87 days) and MST 24 days (range 3‐91 days), with an ORR of 60% and 63% recorded toxicities. However, a proportion of haematological toxicoses may have gone undetected due to the absence of associated clinical signs. The difference in MST and TTP between the 2 groups was not statistically significant. Similarly, no negative prognostic factors were identified. Although responses were generally short lived, this study suggests that TMZ may achieve similar efficacy to TMZ/DOX whilst being associated with a lower frequency of recorded toxicities.