Soft-coated wheaten terriers, German pointers and miniature schnauzers more likely to be diagnosed with phaeochromocytoma.

Several dog breeds have been found to be “ultra-predisposed” for diagnosis of a rare adrenal tumour.

RVC and Utrecht University researchers analysed data from the former’s VetCompass programme to determine breed predispositions and demographic risk factors for phaeochromocytoma (PCC), a rare tumour occurring in both dogs and humans thought to be “substantially under-diagnosed” because of its non-specific clinical signs.

The researchers examined data from 2,250,741 dogs under primary veterinary care in the UK in 2019, with 92 confirmed as PCC cases.

Published in PLOS One, the study found an annual prevalence and annual incidence risk of PCC diagnosis of one per 100,000 dogs, between four-and-a-half and 25 times higher than that reported for human PCC.

Of the 92 confirmed cases, 65 (70.7%) were male (with 75.4% neutered) and 27 (29.4%) were female (with 77.8% neutered), with a median age at first diagnosis of 10.6 years and median adult bodyweight of 12.8 kg.

Predisposition

Three breeds were identified with predisposition for PCC diagnosis; compared with crossbreeds, the soft-coated wheaten terrier (30.9 times), German pointer (11.0) and miniature schnauzer (4.7) were significantly more likely to be diagnosed with PCC.

English cocker spaniels (0.78 times) and Labrador retrievers (0.67) were less likely to be diagnosed with PCC in the findings.

Terrier breeds overall were 1.65 times more likely than non-terrier breeds to be diagnosed, as were breeds predisposed to pituitary/cortisol-secreting cancer (1.64) or pituitary/cortisol-secreting adrenal cancer and/or insulinoma (1.57).

Neutered males were 2.2 times more likely than intact males to be diagnosed, while dogs aged between nine and 15 were 2.4 times more likely than those aged six to nine.

Dogs aged five and under were just 0.07 times as likely to be diagnosed, however the authors acknowledged that age is less likely to be a risk factor specific to PCC and more broadly associated to the diagnosis of a neoplastic disease.

Two purposes

First author Martin Litviakov said: “The findings serve two purposes: firstly, they provide veterinary practitioners, particularly those in first opinion practice, with additional information to help increase their suspicion of phaeochromocytoma earlier in the disease process, hopefully leading to better outcomes; and secondly, they act as a scaffold for future studies in canine phaeochromocytoma, especially when considering its potential as a translational model for the human disease.”

Co-author and RVC professor of companion animal epidemiology Dan O’Neill said the findings could act as an “advanced warning system” for vets and pet owners.

Final author and RVC senior lecturer in small animal soft tissue surgery Floryne Buishard noted the importance of the novel finding that PCC incidence in dogs is significantly higher than in humans.

She said: “This underpins the value of spontaneous canine phaeochromocytoma as a translational study model for human phaeochromocytoma because canine phaeochromocytoma samples are more readily available for molecular studies, unlike human phaeochromocytoma samples.”