A study conducted by UC Riverside found that medium-sized dogs have a higher risk of developing cancer compared to the very largest or smallest breeds. The multistage model of cancer predicts that size is a risk factor for cancer, as larger animals have more cells and a longer lifespan, giving them more opportunities to acquire mutations that lead to cancer. This risk factor is evident within species, with tall humans having a higher cancer risk than shorter individuals. To further investigate these risk factors, the study compared cancer mortality rates in dogs with a wide range of sizes, from tiny chihuahuas to great Danes.
The research revealed that the smallest dogs have around a 10% chance of dying from cancer, while some larger breeds, like the Burmese mountain dog, have over a 40% chance of death from cancer. Flat-coated retrievers and Scottish terriers were identified as outliers in the study, with higher cancer mortality rates than expected for their size. Generally, the study supported the idea that size is a significant risk factor for cancer in dogs. Surprisingly, the very largest breeds, such as great Danes, had lower cancer rates than medium-sized breeds, which was attributed to their shorter lifespan.
The study findings align with the multistage model of cancer acquisition, which suggests that larger size and longer lives provide more opportunities for cells to mutate and develop into cancer. The comparison of different dog breeds helped to illustrate this concept, with the differences in cancer mortality rates reflecting the impact of size variation within a species. This correlation between size and cancer risk does not hold true when comparing different species, as evident in the example of mice and elephants, indicating that cancer prevention mechanisms may evolve differently in various animals.
The study also highlighted the intriguing phenomenon where larger animals, such as elephants, exhibit lower cancer rates despite their increased size and lifespan. This observation raises questions about how these animals have evolved mechanisms to prevent cancer effectively. For instance, whales, which have limited data on cancer occurrences, and elephants, known for their low cancer rates, offer insights into potential biological mechanisms that help prevent cancer in larger species. Understanding these unique adaptations could provide valuable insights into cancer prevention strategies for humans and animals.
Overall, the study shed light on the complex relationship between size, lifespan, and cancer risk in animals, specifically in the context of dog breeds. By exploring how different breeds of dogs with varying sizes experience differences in cancer mortality rates, the research contributed to our understanding of cancer acquisition and prevention mechanisms. The findings suggest that size plays a significant role in cancer risk within species, while also hinting at the potential for evolving cancer prevention strategies in different animal species based on their size and biology.
