Cancer is Common Among Many Animal Species, Yet Science Still Lacks Clarity: Which Animals Are Most Susceptible and Why?
Typically, larger and longer-lived animals are thought to have a higher risk of developing cancer. Their bodies contain more cells, leading to more cell divisions throughout their lifetime. Each cell division carries the potential for mutations, increasing their likelihood of developing cancer.
However, the Peto’s paradox, named after statistician and epidemiologist Richard Peto, suggests otherwise: cancer rates do not correlate with body size.
For instance, the blue whale—the largest animal—seems to rarely develop cancer. In contrast, we record tens of millions of cancer cases each year in humans, according to IFLScience on October 29.
Large animals do not always have a high risk of cancer – (Image: Biodesign Institute at Arizona State University).
So, if not larger animals, which species have the highest cancer risk?
Why Do Elephants Rarely Get Cancer?
Over the past decade, Carlo Maley, the lead author of a study on cancer in the animal kingdom, along with colleagues, has examined more than 16,000 forensic records from 292 species of vertebrates to complete the picture of cancer rates in animals.
The findings suggest that cancer incidence increases with body size, but this increase is minimal and insufficient to refute Peto’s paradox. Concurrently, it appears to support this paradox, as cancer rates tend to decrease in animals with longer gestation periods, a characteristic associated with larger body sizes.
The study indicates that larger animals have evolved mechanisms to suppress cancer. “Larger, longer-lived species invest more in body maintenance. I expect them to have better defenses against cancer, as they need to in order to grow large and live long. From an evolutionary perspective, this is not necessarily a paradox,” said Amy Boddy, another author of the study.
For example, elephants possess 20 copies of the tumor-suppressing gene P53. This is why they rarely develop cancer despite their size.
The research team noted that each species has its own story regarding the reasons and methods they employ to combat cancer. Consequently, cancer rates and survival strategies vary among vertebrate species.
Which Species Are Most Susceptible to Cancer?
Elephants have 20 copies of the tumor-suppressing gene P53 – Image: Shutterstock
The team discovered that some species are at a higher risk of cancer than others. Among those with unusually high cancer rates is the European pine marten (63% chance of developing tumors), marsupials (56%), and hedgehogs (45%).
Conversely, the black-footed penguin has the lowest cancer rate (less than 0.4%), followed by dolphins (under 1.3%) and Rodrigues fruit bats (under 1.6%).
Moreover, mammals generally have the highest rates of both benign and malignant tumors. They are followed by reptiles, birds, and amphibians.
Overall, the study emphasizes that the relationships between size, lifespan, reproductive duration, and cancer resistance are even more complex than we previously thought. By enhancing our understanding of cancer in other species, we may improve our chances of combating this deadly disease in ourselves.
The study is published in the journal Cancer Discovery.
