The GP's point is that you should specifically say metastatic cancer if you want to cite that statistic, not generalize it to cancer.

This might be a stupid question, but doesn't "spread" imply metastasis? It just has better rhyming options.

If it's metastatic, you've had it... doesn't quite trip off the tongue.

Sort of. If it's limited to only metastasis, then the original statement "Much process has been made in heart disease, but cancer?" is pretty silly, as it's comparing the worst of cancer cases with all of heart disease.

spread= metastatic

Yes, I understand that, but your comment is easy to read as being about all cancer, and an awful lot of treatment is done prior to it spreading.

Much process has been made in heart disease, but cancer? Not so much. is really the problem, as early stage treatment has gotten vastly more effective over the last 20 years (My father succumbed to metastatic cancer in 1994, I pay some attention to the overall progress in addressing cancer).