Comparison of 3 Protocols for Treatment after Induction of Remission in Dogs with Lymphoma

Background: The optimal treatment after inducing complete remission (CR) in dogs with lymphoma has not been established. Hypothesis: After inducing CR with L‐asparaginase, vincristine, cyclophosphamide, doxorubicin, prednisone (L‐CHOP); consolidation with either half‐body radiation therapy (HBRT); or lomustine (CCNU) and mechlorethamine, vincristine, procarbazine, prednisone (MOPP) would improve first remission duration compared with continuing a CHOP‐based protocol for an additional 4 months. Animals: Dogs with stage III‐V lymphoma. Methods: Prospective clinical trial in which dogs initially were treated with an 8‐week induction protocol that consisted of L‐CHOP. Dogs in CR after induction were then allocated to 1 of 2 consolidation arms. A chemotherapy consolidation arm consisted of 2 treatments with CCNU and 1 cycle of MOPP. A HBRT arm consisted of 2 sequential 8.0‐Gy fractions to the cranial and caudal half‐body separated by 30 days. Vincristine was given between fractions. Results of the consolidation arms also were compared with a historical group treated with the same 8‐week induction protocol followed by CHOP therapy until week 24. Results: Overall, 67% of the dogs were in CR after 8 weeks of induction chemotherapy and were compared. Fifty‐two dogs were in the historical arm, 23 in the CCNU/MOPP arm, and 27 in the HBRT arm. No difference in first remission duration was found among groups. Median first remission duration for the historical, CCNU/MOPP, and HBRT arms were 307, 274, and 209 days, respectively (P= .28). Overall second CR rate was 82% and was not different among groups (all P > .58). Overall remission duration (P= .28) and survival time (P= .48) were not different among groups. Conclusions and Clinical Importance: Consolidation with either CCNU/MOPP or HBRT showed no advantage over a standard CHOP‐based protocol.