Cancer screening is gaining interest in veterinary medicine, as it is the leading cause of death in older dogs. The Dog Aging Project (DAP) reported a 3.0% prevalence of malignant tumor diagnoses within a cohort of 27,541 dogs, which is lower than the prevalence reported in countries with national veterinary cancer registries. A study was conducted to assess the rate of undiagnosed malignant neoplasms in middle- to older-aged dogs and identify the diagnostic methods most commonly used to detect these cancers.
The study included 902 older, healthy dogs, with results showing that the prevalence of occult malignant neoplasia ranged from 2.7% to 6.0%, including both definitively diagnosed and suspected cases of cancer. The majority of these tumors were detected through physical examination and confirmed using fine-needle aspiration (FNA) and cytology. Dogs diagnosed or suspected of having cancer were statistically older than those without suspected cancer, with a median age of 8 years compared to 7 years, respectively.
When combining physical examination with cytologic assessment of dermal and subcutaneous masses, 83% of cancers were definitively diagnosed. However, this rate dropped to 50% when including both definitive diagnoses and suspected cases of cancer. This decrease may be attributed to the higher cost and perceived invasiveness of more advanced diagnostic procedures, such as ultrasound-guided aspirates, which some pet owners declined. Additionally, not all dogs underwent full staging if cancer was detected on initial screening, as they had already failed the screening process.
The study highlights the importance of routine physical examinations, particularly in older dogs, for detecting cancer, especially apocrine gland anal sac adenocarcinomas. However, several limitations should be considered, such as the VACCS eligibility criteria restricting enrollment to certain breeds and the potential overestimation of cancer prevalence in a more diverse population.
