July 9, 2025, 10:01 am | Read time: 4 minutes
Cancer is not only a serious issue for humans—it increasingly affects pets as well. A new study from Spain provides the first comprehensive overview of canine tumors over a ten-year period. The findings shed light on the actual scope, the most common types of cancer, and how animals are treated in practice—offering surprising insights for veterinarians and pet owners.
A research team from the University of León (Spain) conducted a retrospective study evaluating all cancer cases diagnosed between 2015 and 2024 at the small animal clinic of the University Hospital (HVULE). The study provides important insights into the cancer risk of certain dogs and was published in the journal “Frontiers in Veterinary Science.”
A total of 123 cases were analyzed, including 107 dogs and 16 cats. The aim was to gain a realistic overview of the affected animal species, tumor types, and treatment strategies. The investigation offers rare insights into the oncological care of pets in clinical practice. It also highlights where data gaps exist.
About One in Four Dogs Develops Cancer During Their Lifetime
Cancer is one of the most common causes of death in pets. This is partly due to the increased life expectancy of dogs and cats. While this is initially a positive effect of improved veterinary medicine, nutrition, and more intensive care by pet owners, the risk of tumor diseases also increases with age.
According to the Veterinary Cancer Society, about one in four dogs develops cancer during their lifetime. In countries like the United Kingdom or Australia, there are central databases for recording veterinary cases. However, in other countries, including Spain, standardized tumor registries are lacking. This study aims to fill this gap for a region in Spain and gain insights into the actual occurrence and management of cancer in pets.
The research team examined the clinical data of all dogs and cats diagnosed with tumors from 2015 to 2024 at the small animal clinic of the University Hospital of León (HVULE). The basis was a systematic evaluation of electronic medical records. The study collected demographic data such as
- Age
- Gender
- Breed
- Size
- Weight
- Tumor type
- Location
- Histology (tissue type)
- Therapy form
- Concomitant medication
- Side effects
Most Tumors Were Malignant
Out of 22,987 treated pets, the researchers identified 123 cases with tumor diagnoses. This corresponds to an annual incidence of 530 tumor cases per 100,000 animals. Eighty-seven percent of the affected animals were dogs, 62.6 percent were female, and 77.2 percent were purebred. Older animals were particularly at risk—78.9 percent were classified as “senior” or “geriatric.”
Most tumors were malignant (87.8 percent), originated from epithelial tissue (40.7 percent), and were primarily found in the mammary gland (27.6 percent) or skin (26.8 percent). Carcinomas (35.8 percent) and lymphomas (19.5 percent) were the most common tumor types.
Almost half of the animals underwent surgery (42.3 percent), and 37.4 percent received chemotherapy—mostly administered orally, often with the protein kinase inhibitor Toceranib. Euthanasia was applied to 26.8 percent of the animals. Side effects such as neutropenia and vomiting occurred in 43.5 percent of the animals treated with chemotherapy.
Primarily Older, Female, and Purebred Dogs Affected
The results show that cancer in pets primarily affects older, female, and purebred dogs. The high rate of malignant tumors underscores the importance of early detection and therapy. With an incidence rate comparable to other European studies, this analysis not only provides an important reference value for Spain. It is one of the few long-term studies in the field.
Although the data cannot be directly applied to Germany, they show parallels with the veterinary findings here. For example, mammary tumors in female dogs are also considered one of the most common tumor diseases.1 It is therefore assumed that older, female, and purebred dogs also have an increased cancer risk here.
Study Has Limited Significance
The study provides an overview of cancer diagnoses and therapies in a Spanish small animal clinic over an extended period for the first time. However, as a retrospective analysis, it is subject to typical limitations: Some cases were excluded due to missing important data. The small number of cases in cats (only 16) limits the significance for this species.
Additionally, it is a regional survey; the results cannot be easily generalized to all of Spain or other countries. The impact of the COVID-19 pandemic on veterinary visits was recognized as a potential confounding factor. Social aspects, such as the owners’ willingness to pay and related therapy decisions, could not be considered. Nevertheless, the study provides valuable, previously unavailable insights into the oncological care of pets and the cancer risk for certain dogs.
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Regular Check-Ups for Older Animals Could Save Lives
The study from the University of León provides the first solid data on the frequency and treatment of tumors in pets in Spain. Primarily, older, female, and purebred dogs are affected, mostly with malignant tumors of the mammary gland or skin. Surgical interventions were the most common form of treatment, followed by oral chemotherapy. The study shows the importance of clinical case analyses. For pet owners, this means: Regular check-ups for older animals could save lives.