Aim: Recent trends in comparative animal and human research inform us that collaborative research plays a key role in deciphering and solving cancer challenges. Globally, cancer is a devastating diagnosis with an increasing burden in both humans and dogs and ranks as the number three killer among humans in Kenya. This study aimed to provide comparative information on cancers affecting humans and dogs in Nairobi, Kenya.

Materials and Methods: Dog data collection was by cancer case finding from five veterinary clinics and two diagnostic laboratories, whereas the human dataset was from the Nairobi Cancer Registry covering the period 2002-2012. The analysis was achieved using IBM SPSS Statistics® v.20 (Dog data) and CanReg5 (human data). The human population was estimated from the Kenya National Census, whereas the dog population was estimated from the human using a human:dog ratio of 4.1:1.

Results: A total of 15,558 human and 367 dog cancer cases were identified. In humans, females had higher cancer cases 8993 (an age-standardized rate of 179.3 per 100,000) compared to 6565 in males (122.1 per 100,000). This order was reversed in dogs where males had higher cases 198 (14.9 per 100,000) compared to 169 (17.5 per 100,000) in females. The incident cancer cases increased over the 11-year study period in both species. Common cancers affecting both humans and dogs were: Prostate (30.4, 0.8), the respiratory tract (8.3, 1.3), lymphoma (5.6, 1.4), and liver and biliary tract (6.3, 0.5), whereas, in females, they were: Breast (44.5, 3.6), lip, oral cavity, and pharynx (8.8, 0.6), liver and biliary tract (6.5, 1.2), and lymphoma (6.0, 0.6), respectively, per 100,000.

Conclusion: The commonality of some of the cancers in both humans and dogs fortifies that it may be possible to use dogs as models and sentinels in studying human cancers in Kenya and Africa. We further infer that developing joint animalhuman cancer registries and integrated cancer surveillance systems may lead to accelerated detection of the risks of cancer in Africa.

Keywords: Africa, cancer, cancer registry, comparative oncology, Kenya, Nairobi, One Health.

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