Breed predisposition to canine gastric carcinoma – a study based on the Norwegian canine cancer register – PMC

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Canine gastric cancer is rarely diagnosed and is reported to account for approximately 0.1-0.5% of canine neoplasms [1-3]. however, it is still more prevalent in dogs than in other domestic animals [4]. the majority of gastric malignancies in dogs are carcinomas, accounting for 50-90% [2,5,6], followed by leiomyosarcomas and malignant lymphomas [2]. adenocarcinoma is the most common type of gastric carcinoma [2]. this subtype of carcinoma forms tubular structures and can exhibit various patterns at different levels of invasion of the stomach wall. undifferentiated carcinomas, which comprise the remaining carcinomas, have no visible glandular structures [4]. The clinical relevance of these histopathologic subtypes of carcinoma is unknown, and the general term “gastric carcinoma” is used in this article. among dogs, gastric carcinoma has been reported to affect males more frequently than females [2,3,6-9]. a higher incidence among men is also observed for human gastric carcinoma [10]. gastric carcinoma is generally a disease of older dogs, but has been reported in dogs between 3 and 20 years of age, with a mean age at diagnosis of 8.4 to 10.8 years [2,3,5 ,7-9,11,12]. the incidence of gastric carcinoma increases with age also in humans [10]. gastric carcinoma in dogs is most often located in the lesser curvature and pyloric region of the stomach [2,3,5,8].

The most common clinical signs associated with gastric carcinoma are vomiting, anorexia, and weight loss. hematemesis, melena, anemia, lethargy, ptyalism, polydipsia, abdominal distention, and abdominal discomfort are other reported signs [3,5,6,8,9]. clinical signs resemble those associated with chronic gastritis [13]. most canine patients have had clinical signs for approximately four months or less at diagnosis, although durations of up to 18 months have been reported [3,5,6,8,14]. the prognosis in cases of gastric carcinoma is poor. one case series reported a median survival of 35 days, with a range of 0 days to 10 months after diagnosis [5]. furthermore, 70-90% of gastric carcinomas have metastasized at the time of diagnosis or euthanasia [3,5,7]. the most common reported sites for metastases are the regional lymph nodes, with others including the omentum, duodenum, liver, pancreas, spleen, esophagus, adrenal glands, and lungs [3,5,7,9] .

Reading: Gastric carcinoma in dogs

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Usually, a preliminary diagnosis of canine gastric carcinoma is made by ultrasound or endoscopic examination of the stomach. using ultrasound, gastric wall thickening, loss of gastric wall layers, and regional lymph node enlargement are likely to be seen [15]. endoscopy allows the visualization of the mucosa and the performance of biopsies in order to enable a definitive diagnosis. a distinct ulcer with thick, irregular walls raised from the surrounding area is commonly seen, but more diffuse changes with loss of rough folds and submucosal vascular pattern in the absence of ulcers are also described [3,8].

In humans, 95% of gastric cancers are sporadic cases, and Helicobacter pylori infection is the most important environmental risk factor [16]. familial aggregation in a small proportion of cases suggests a significant genetic predisposition [17,18]. hereditary diffuse gastric cancer in humans, where the causative germline mutation has been identified as cdh1, is reported to be associated with 5% of all gastric cancers [17].

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A canine breed predisposition for some types of cancer has been reported [1]. although breed predisposition to gastric carcinoma has been suspected, several studies have failed to provide supporting evidence [2,5,9]. Table 1 provides a summary of predisposed breeds reported from other studies, most of which are case series. these case series are purely descriptive studies, with no comparison between subgroup characteristics. due to this limitation, no assumption can be made about associations between exposure and outcome [19]. other investigators have conducted case-control studies based on hospital records [3,12]. there is no knowledge of the population at risk from which the cases arise in this design. therefore, they cannot be used to estimate cancer incidence, although the odds ratio for cancer by race can be estimated [20].

Because of the advanced stage of the disease at diagnosis and the high frequency of metastases, early detection is essential if treatment of canine gastric cancer is attempted. Because the presenting signs may be similar to those seen in chronic gastritis, some patients receive symptomatic treatment for gastritis for prolonged periods. suspicion of gastric cancer may first arise when this form of treatment fails. therefore, it is important for animal welfare to obtain a correct diagnosis as soon as possible. better knowledge of the breeds at risk may allow early detection of gastric carcinoma in affected cases and may also facilitate comparative genetic studies that could identify factors that contribute to the development of gastric cancer.

We hypothesized that there is a breed predisposition to canine gastric carcinoma in dogs. The aim of the study was to retrospectively investigate the proportion and possible breed predisposition to canine gastric carcinoma using data from the Norwegian Canine Cancer Registry as a basis for calculating PMR for the period 1998-2009.

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