Epirubicin in the treatment of canine histiocytic sarcoma: sequential, alternating and rescue chemotherapy.

The aims of this study were to report treatment outcomes for dogs with histiocytic sarcoma (HS) treated with both lomustine and epirubicin, and to report response rates to epirubicin as a rescue therapy in dogs previously treated with lomustine. Medical records of dogs with a diagnosis of HS that were treated with both lomustine and epirubicin were retrospectively evaluated. Of 29 dogs receiving epirubicin alternating with, or subsequent to lomustine treatment, including in a rescue setting, response to epirubicin could be assessed in 20 with an overall response rate (ORR) of 29% and biological response rate (BRR) of 71%. Median time to progression (TTP) in 12 of these 20 dogs in which it was assessable was 69 days (range: 40-125 days). For dogs treated in the rescue setting epirubicin specific ORR was 19% and BRR 63%. Median TTP in the 9 of these 16 dogs in which it was assessable was 62 days (range: 40-125 days). Median survival time for all dogs treated with both epirubicin and lomustine was 185 days (range: 27-500 days). Some dogs with HS respond to epirubicin and dogs treated with combinations of epirubicin and lomustine have modestly improved survival times compared with single agent studies, and similar to dogs with HS treated with alternating lomustine and doxorubicin. Single agent epirubicin is also a valid short term rescue therapy for canine HS.