Outcomes and survival times of client-owned rabbits diagnosed with thymoma and treated with either prednisolone or radiotherapy, or left untreated

Abstract Background Thymomas are diagnosed with relative frequency in the pet rabbits (Oryctolagus cuniculus domesticus). There is currently limited knowledge about treatment and survival times for rabbits affected by this neoplasm. The goals of this study were to evaluate the survival times of rabbits with highly suspected or confirmed thymoma undergoing different treatment options compared to no treatments elected. Methods This retrospective study examined the clinical outcomes and survival times associated with two non-surgical treatment options, intensity-modulated radiotherapy (IMRT) (n=5) and prednisolone therapy alone (n=18). A cohort of rabbits that received no treatment (n=10) was also evaluated and used for comparison. Individuals were monitored for clinical change with these treatments until the time of their death or euthanasia. Results IMRT resulted in improvement of clinical signs, objective tumor responses and moderate average survival times with minimal side effects for those individuals that completed the treatment course. However, one rabbit died from anesthetic complications during IMRT, and overall survival times did not differ significantly from the no treatment group. Glucocorticoid therapy alone, on average, also reduced clinical signs associated with thymoma with minimal side effects. Survival times of rabbits who were administered prednisolone alone were significantly longer compared to those of rabbits receiving no treatment. Conclusions and clinical relevance This study illustrates cases of significant improvement in the size of thymoma in those who survived the full course of treatment with radiation but highlights the risks that are always involved with this treatment option in this species and illustrates that this may ultimately limit patient's life expectancy. This study shows that prednisolone alone may significantly extend survival time and improve quality of life in rabbits with thymoma and provides owners with an additional low-cost, effective option for treating this neoplasm with minimal side effects shown in this population.