If larger animals had better cancer fighting weapons, then the largest animals ever on the planet, the blue whale, being 15-25x larger, would have that much better cancer fighting weapons. I wonder what those would be.
They needed to evolve to reach a certain age ( -> once they cant reproduce anymore) without dying to cancer. https://www.youtube.com/watch?v=fMMPKJFYzdY for a more in depth explaination