Bigger Bodies, Bigger Cancer Risk? New Study Challenges Old Beliefs

For decades, experts believed larger animals were no more susceptible to cancer than smaller ones. However, new research has turned that notion on its head. This means larger animals like elephants, giraffes and pythons get more cancer than tiny creatures like bats, mice and frogs. A team from the University of Reading, University College London, and the Johns Hopkins University School of Medicine examined data from 263 species of mammals, birds, reptiles, and amphibians. Their findings call into question Peto's paradox, which proposed in 1977 that an animal's size had no influence on cancer risk.

Large Animals at Greater Risk of Cancer

The study, published in the Proceedings of the National Academy of Sciences (PNAS), discovered that larger species have a consistently greater tumor prevalence (1^✔ ✔Trusted Source
No evidence for Peto's paradox in terrestrial vertebrates

Go to source). However, species that evolved quickly to great sizes, such as elephants, developed stronger natural cancer defense mechanisms.

Professor Chris Venditti, a senior researcher at the University of Reading, stated, "Everyone knows the myth that elephants are afraid of mice, but when it comes to cancer risk, mice have less to fear." We've proven that larger animals, such as elephants, have greater cancer rates- as you'd expect given how many more cells may go wrong."

The study analyzed the largest dataset of its kind, which included veterinarian autopsy records from 31 amphibians, 79 birds, 90 mammals, and 63 reptiles. Despite differences in development patterns, with some species expanding forever and others halting at maturity, the tendency remained consistent: larger animals had more cancer. However, species such as elephants have found strategies to decrease tumors, keeping their risk equivalent to much smaller animals such as tigers.

Dr. Joanna Baker, a co-author from the University of Reading, noted, "When species needed to grow larger, they evolved remarkable cancer defenses." Elephants should not be afraid of their size; they evolved powerful biological tools to combat disease."

Do Humans Fit Into the Size-Cancer Equation?

Humans see a complex image. Medical developments make it difficult to know where we fall in the size-cancer equation. The study verifies a general trend: larger species are more likely to develop cancer, but it also shows how some have evolved to combat this. Understanding these natural defences could lead to new cancer treatments.

The investigation also found some surprising exceptions. The common budgie (Melopsittacus undulatus), a small bird weighing less than 30 grams, had a cancer risk 40 times greater than expected. Meanwhile, the naked mole rat (Heterocephalus glaber) appears to be virtually completely cancer-resistant.

Dr. George Butler, main author from University College London and Johns Hopkins, stated, "Finding which animals are naturally better at fighting cancer opens up exciting new avenues for research." By researching these successful species, we can gain a better understanding of how tumors arise and potentially find novel ways to combat the disease."

Reference:

1. No evidence for Peto's paradox in terrestrial vertebrates - (https://www.pnas.org/doi/10.1073/pnas.2422861122)

Source-Medindia