Cancer Incidence in Pet Dogs: Findings of the Animal Tumor Registry of Genoa, Italy

Abstract

Background: The occurrence of spontaneous tumors in pet animals has been estimated in a few European and North American veterinary cancer registries with dissimilar methodologies and variable reference populations. Objectives: The Animal Tumor Registry (ATR) of Genoa, Italy, was established in 1985 with the aim of estimating the occurrence of spontaneous tumors in dogs. Methods: Six thousand seven hundred and forty-three tumor biopsy specimens were received from local veterinarians in the Municipality of Genoa between 1985 and 2002. Three thousand and three hundred and three (48.9%) biopsy specimen samples were diagnosed as cancer and were coded according to the International Statistical Classification of Diseases (ICD-9). Results: Mammary cancer was the most frequently diagnosed cancer in female dogs, accounting for 70% of all cancer cases. Incidence of all cancers was 99.3 per 100,000 dog-years (95% CI: 93.6–105.1) in male dogs and 272.1 (95% CI: 260.7–283.6) in female dogs. The highest incidence rates were detected for mammary cancer (IR = 191.8, 95% CI: 182.2–201.4) and for non-Hodgkin's lymphoma (IR = 22.9, 95% CI: 19.7–26.5) in bitches and for non-Hodgkin's lymphoma (IR = 19.9, 95% CI: 17.4–22.7) and skin cancer (IR = 19.1, 95% CI: 16.6–21.8) in male dogs. All cancer IR increased with age ranging between 23.7 (95% CI: 18.4–30.1) and 763.2 (95% CI: 700.4–830.1) in bitches and between 16.5 (95% CI: 12.8–21.1) and 237.6 (95% CI: 209.1–269.0) in male dogs aged ≤3 years and >9–11 years. Conclusion: This study summarizes the work done by the ATR of Genoa, Italy, between 1985 and 2002. All cancer incidence was 3 times higher in female than in male dogs, a difference explained by the high rate of mammary cancer observed in bitches. Because a biopsy specimen was required to make a cancer diagnosis, cancer rates for internal organs cancers, such as respiratory and digestive tract cancers may have been underestimated in the study population.