Actinomycin D as rescue therapy in dogs with relapsed or resistant lymphoma: 49 cases (1999--2006)

To evaluate response rate and disease-free interval in dogs with relapsed or resistant lymphoma treated with actinomycin D, determine hematologic toxicoses, and identify prognostic factors associated with response to treatment.

Retrospective case series.

49 dogs with relapsed or resistant lymphoma.

Medical records were reviewed for information regarding signalment, physical examination findings, results of diagnostic testing, substage, previous chemotherapy, previous treatment with prednisone, actinomycin D dosage, number of doses administered, response, disease-free interval, and results of CBCs performed after treatment.

Actinomycin D was administered at a median dosage of 0.68 mg/m2 (range, 0.46 to 0.72 mg/m2), IV, every 3 weeks for 5 treatments or until disease progression. Twenty-six (53%) dogs received prednisone concurrently. Twenty (41%) dogs had a complete remission, and median disease-free interval in these dogs was 129 days. Thrombocytopenia was the most common hematologic toxicosis (n = 22 [45%]). Concurrent prednisone administration, a shorter duration of first remission, and an increased number of previous chemotherapy agents were significantly associated with a lower likelihood of responding to actinomycin D treatment. Concurrent prednisone administration and an increased number of previous chemotherapy agents were significantly associated with a shorter disease-free interval.

Results suggested that administration of actinomycin D as a single agent was effective for rescue chemotherapy of dogs with relapsed or resistant lymphoma and that treatment was well tolerated, although mild thrombocytopenia developed commonly.