That was the follow up question I was going to ask actually, about blue whales and how they have more cells which sensically would make you assume its easier for them to get cancer, but as you said, it's not very well researched. I saw a while ago a kurzgesagt video which I can't find which theorised that big animals such as whales get hypertumors often which kill their cancers and create a rate more even with the rest of us. Maybe that's why.