Treatment of feline oral squamous cell carcinoma with accelerated radiation and carboplatin with and without follow-up toceranib phosphate

ObjectivesOral squamous cell carcinoma (SCC) is the most common oral tumor in cats but treatment options that provide long-term tumor control are limited. Radiation therapy is a reported treatment option, but local tumor control is still difficult to obtain and additional treatment options are needed. Toceranib phosphate recently emerged as having biologic activity against feline oral SCC. This study is a preliminary evaluation of radiation therapy and toceranib phosphate in cats with oral SCC.MethodsThis non-blinded, retrospective, single-institutional study included all patients between 2011 and 2023 that underwent the same treatment with accelerated radiation therapy and concurrent carboplatin as previously described, with the exception of one additional fraction of radiation. Once the early side effects abated, toceranib phosphate was offered as follow-up maintenance therapy. The median survival time (MST) and progression-free interval (PFI) were assessed for the cats that received toceranib after radiation therapy and carboplatin, and were compared with the cats that received the same radiation and carboplatin protocol within the same time period but did not receive follow-up toceranib.ResultsOverall, 47 cats met the criteria for evaluation; of them, 15 received follow-up toceranib. The MST of all cats was 164 days; there was no significant difference in MST or PFI between the cats that did and did not receive adjuvant toceranib (MST 208 days vs 162 days, respectively; <i>P</i> = 0.35). When comparing cats with lingual tumors, the PFI was significantly longer in the cats that received toceranib than those that did not (142 days vs 104 days, respectively; <i>P</i> = 0.045); however, there was no difference in MST (197 days vs 147 days; <i>P</i> = 0.15).Conclusions and relevanceThis study suggests that most cats with oral SCC do not benefit from toceranib after radiation therapy. There may be clinical benefit to administering adjuvant toceranib after radiation in cats with lingual SCCs, but the mechanism remains unclear and additional studies are warranted.