If this increased cancer rates, whales should be completely consumed by cancer at a young age.
However, there are few cases of whales being found to die of cancer.
However, there are few cases of whales being found to die of cancer.
Further reading: http://www.nature.com/news/how-elephants-avoid-cancer-1.1853...
There are a number of ways that whales are different from humans, and there is no reason that the cancer scaling with mass in humans is invalidated by whales.
But, if the GP's hypothesis were to be empirically tested, I guess they could correct for the weight or volume of the individuals being sampled.