Multiple malignant primary tumors in dogs: an Italian registry-based epidemiological study

Area of Science:

• Veterinary Oncology
• Epidemiology
• Comparative Oncology

Background:

• Human oncology recognizes increased risk of subsequent malignancies after a primary cancer diagnosis.
• Registry-based studies on multiple malignant primary tumors (mMPTs) in dogs are limited.
• Increasing canine longevity and advanced treatments necessitate understanding mMPTs' epidemiology and biology.

Purpose of the Study:

• To assess the occurrence and patterns of mMPTs in dogs with malignant tumors.
• To analyze data from four Italian regional cancer registries (2013-2024) via the NILOV network.
• To identify factors associated with mMPTs in the canine population.

Main Methods:

• Analysis of 16,618 canine cancer records using the Vet-ICD-O-Canine-1 system.
• Estimation of proportional morbidity ratios (PMRs) using multilevel mixed-effects Poisson regression.
• Evaluation of tumor histotype associations via chi-squared tests and network co-occurrence analysis (netCoin).

Main Results:

• mMPTs were found in 11.3% of canine cancer cases, influenced by age and sex.
• Risk of mMPTs increased with age, peaking in dogs ≥12 years (PMR ≈ 7.3).
• Females had a slightly higher risk (PMR ≈ 1.3); breed had minimal effect; network analysis revealed non-random tumor clustering.

Conclusions:

• This study is the first large-scale, registry-based analysis of mMPTs in Italian dogs.
• Multiple malignancies are common in dogs, primarily influenced by age and sex.
• Findings support the utility of integrated veterinary cancer registries and comparative oncogenesis studies.