Medium-Sized Dogs Face Higher Cancer Risk

Researchers from the University of California, Riverside, have discovered that medium-sized dogs are more susceptible to cancer compared to the largest and smallest breeds. The study, recently published in the journal Royal Society Open Science, aimed to validate the "multistage model," a theory suggesting that body size plays a role in cancer development. While the hypothesis was confirmed, the study also considered variations in body size within the same species.

The replication of cells often leads to errors or mutations. Animals with larger bodies and longer lifespans have more cells and longer cell division cycles, increasing the probability of developing mutations that can lead to cancer. To explore these risk factors further, the researchers focused on dogs due to their diverse range of body sizes.

By analyzing three different datasets on dog mortality, the researchers found that smaller breeds like Pomeranians, Shih Tzus, and Chihuahuas had a roughly 10% chance of dying from cancer. On the other hand, larger breeds like Burmese Mountain Dogs had a greater than 40% chance of succumbing to cancer. Interestingly, the largest dog breeds, such as Great Danes, exhibited relatively lower rates of cancer. This aligns with the commonly observed but not fully understood trend where a dog's life expectancy generally decreases as its size surpasses a certain threshold.

These findings support the multi-stage model of cancer development, indicating that larger bodies and longer lifespans provide more opportunities for cell division and consequently increase the likelihood of mutations leading to cancer.