Which animals are susceptible to cancer?

Cancer is common in many animals, but science still has many unknowns, such as which animals are susceptible to cancer and why?

It is logical that animals that live longer and have larger bodies are at higher risk of cancer. They have more cells in their bodies, so they undergo more cell divisions during their lifetime. Each cell division has the potential to cause mutations, so they are more likely to develop cancer.

However, the Peto paradox — named after statistician and anthropologist Richard Peto — suggests that this is not true: cancer rates do not correlate with body size.

For example, the blue whale - the largest animal - seems to rarely get cancer. Meanwhile, we record tens of millions of cancer cases in humans every year, according to IFLScience on October 29.

Large animals are not always at high risk for cancer - (Photo: Biodesign Institute at Arizona State University).

So if not large animals, which species have the highest risk of cancer?

Why do elephants rarely get cancer?

Over the past 10 years, Carlo Maley, lead author of the study on cancer in the animal kingdom, and his colleagues have examined more than 16,000 forensic records of 292 vertebrate species to complete the picture of cancer rates in animals.

Accordingly , cancer incidence increases with body size, but this increase is very small and not enough to refute the Peto paradox. At the same time, seemingly supporting the paradox, cancer incidence tends to decrease in animals with longer gestation periods, which is associated with having larger bodies.

The study found that large animals have evolved mechanisms to suppress cancer . "Bigger, longer-lived species invest more in body maintenance. I would expect them to have better defenses against cancer, because they have to do that to grow big and live long. Evolutionarily, this is not really a paradox ," said Amy Boddy, another author of the study.

For example, elephants have 20 copies of the tumor suppressor gene P53. This is why they rarely get cancer despite their size.

Each species has its own story about why and how it needs to fight cancer, so cancer rates and survival strategies vary across vertebrates, the researchers said.

Which species is most likely to get cancer?

Elephants have 20 copies of the tumor suppressor gene P53 - Photo: Shutterstock

The team found that some species had a higher risk of cancer than others. Among those with unusually high cancer rates were ferrets (63% chance of developing tumors) , opossums (56%) and hedgehogs (45%).

In contrast, black-footed penguins had the lowest cancer rates (less than 0.4%) , followed by dolphins (less than 1.3%) and Rodrigues fruit bats (less than 1.6%).

Additionally, mammals have the highest incidence of both benign and malignant tumors, followed by reptiles, birds, and amphibians.

Overall, the study highlights that the relationship between size, lifespan, reproductive time, and cancer resistance is more complex than we thought. By advancing our understanding of cancer in other species, we may improve our chances of combating this deadly disease in ourselves.

The study was published in the journal Cancer Discovery .