Thymoma Survival in Rabbits

In the literature

Palmer A, Wu CC, Miwa Y, Turek M, Sladky KK. Outcomes and survival times of client-owned rabbits diagnosed with thymoma and treated with either prednisolone or radiotherapy, or left untreated. J Exotic Pet Med. 2021;38:35-43.

The Research …

Thymoma is a relatively common tumor diagnosed in pet rabbits that is typically benign, but expansive growth can lead to clinical signs (eg, dyspnea, exophthalmia, third eyelid protrusion). Other nonspecific clinical signs can include anorexia and lethargy.

Information comparing survival times following radiation therapy, prednisolone monotherapy, or no treatment is limited for rabbits with thymoma. 

This study retrospectively reviewed the medical records of 33 rabbits with thymomas from 2 veterinary hospitals. Of the 33 rabbits, 23 were tentatively diagnosed based on imaging and cytology, and 10 were presumptively diagnosed based on imaging and clinical signs. Respiratory signs ranging from mild to severe were seen in 25 rabbits, 7 of which also had bilateral exophthalmia. The remaining rabbits did not have clinical signs attributed to thymoma.

Five rabbits received radiation therapy, 18 received prednisolone monotherapy, and 10 did not receive treatment. Median survival time was longest for the prednisolone monotherapy group (270 days; range, 144-303 days), followed by the radiation therapy group (213 days; range, 64.2-734 days) and the group that did not receive treatment (92 days; range, 55.7-122 days). There was no significant difference in survival rates between the radiation therapy group and the groups receiving prednisolone monotherapy or not treated; however, survival was significantly longer in the prednisolone monotherapy group than in the group that did not receive treatment.

Histopathology confirming diagnosis of thymoma was only noted in 3 rabbits. The study’s small number of patients, particularly in the radiation therapy group, and lack of treatment randomization may have impacted results.

… The Takeaways

Key pearls to put into practice:

• Oral prednisolone monotherapy seems to be well tolerated by rabbits with thymomas and, in this study, led to significantly longer survival times than rabbits not receiving treatment.

• Additional research is needed to determine whether radiation therapy increases survival times compared with untreated rabbits with thymomas.

• Risks of repeated anesthesia in rabbits treated with radiation therapy should be considered when determining management.