Is CCNU (lomustine) valuable for treatment of cutaneous epitheliotropic lymphoma in dogs? A critically appraised topic

Background: CCNU and other treatment protocols are commonly offered to owners for the treatment of dogs diagnosed with cutaneous (epitheliotropic) T-cell lymphoma (CTCL). Chemotherapy protocols provide variable benefits; they have different side-effects, and they typically require monitoring to detect drug toxicity at a non-negligible cost to the owner. At this time, even though CCNU is most often recommended to treat dogs with CTCL, there is no clear consensus on the benefit of this drug. Knowing which chemotherapy protocol yields the highest rate of complete remission and longest survival times would help veterinarians and pet owners select treatment options based on the best evidence available. Our objective was to review the literature to compare the complete remission rates and survival times of CCNU-based protocols to those of other interventions. We critically assessed the data included in articles reporting treatment outcome in at least five dogs with CTCL. Single case reports and case series with less than five patients were not reviewed to avoid anecdotal evidence of lower quality. Results: The search for, and review and analysis of, the best evidence available as of February 8, 2017, suggests that CCNU and pegylated liposomal doxorubicin appear to yield the highest rate of complete remission in approximately one-third of dogs with CTCL. Other treatment protocols did not report usable information on remission rates. Without any treatment, the mean/median survival time in dogs with CTCL varied between 3 and 5 months. With CCNU protocols, the median survival time was 6 months and the one with retinoids (isotretinoin and/or etretinate), PEG L-asparaginase or prednisolone monotherapy was 11, 9 and 4 months, respectively; all these durations were obtained from small numbers of dogs, however. Conclusions: CCNU leads to a complete remission of signs in approximately one-third of dogs with CTCL, but such remissions are of short duration. The median survival time after CCNU appears longer than that without treatment, but other drugs appear to provide a better long-term prognosis. Further studies are required to investigate the effect of CCNU, alone or in combination, on remission rates, survival times and impact on quality of life.