The aim of this retrospective study was to evaluate the role of palliative radiation therapy in the management of oral lymphoma in dogs. The clinical records of dogs referred to the Oncology Unit at the Animal Health Trust between January 2002 and January 2007 revealed a total of seven dogs that were presented for the treatment of oral lymphoma. Inclusion criteria for this study were disease confined to the mouth, or mouth and submandibular lymph nodes which was confirmed by histopathology and/or immunohistochemistry as lymphoma.

Histopathology was consistent with epitheliotropic lymphoma in four cases, lymphoma in one case, and round cell tumour in two cases. Immunohistochemistry was performed in five cases; three were T cell lymphoma, one T and B cell lymphoma and one null cell lymphoma. Two of seven had local lymph node biopsy and four had regional lymph node aspiration. In all cases, initial staging included haematology, biochemistry, thoracic radiographs and abdominal ultrasound.

Radiation therapy was initiated between 1 to 149 days after referral (mean 27, median 7 days) and between 1 to 157 days from diagnosis (mean 37, median 13 days). Coarse fractionated radiotherapy was administered using a 4MeV linear accelerator. Between three and five fractions of between 500 and 900 cGy were given every 7 days to a total dose of 240 to 360 cGy, with the field delineated by an area 2 to 3 cm from the site of the lesion(s) in all directions.

None of these dogs was lost to follow-up, with a mean and median follow-up time of 683 and 464 days, respectively (range 236 to 1886). Survival times were calculated from date of diagnosis until 31st July 2007.

Four dogs went into complete remission and three had a partial remission of clinical signs. Of the four that went into complete remission three are still alive and disease free 464, 1107 and 1886 days from diagnosis and the other died after 325 days from an unrelated disease in complete remission. The median survival time for the 3 dogs that had partial remission was 243 days (range 236 to 325).

In conclusion, the findings of this small retrospective study showed that radiotherapy can play a role in the successful management of oral lymphoma.

We thank Cambridge University for the use of the linear accelerator.