I'm guessing, since they don't state it clearly, that the combined rate of all cancers is falling, it's only when you look at subsets that it's rising.

Which prompts the idea: "do different cancers compete for shared resources?"

Would a lung cancer use up something that would prevent a different kind of cancer and so once smoking goes out of fashion you get some rebound as other cancers step into the gap left by them?

edit: I looked at the paper and then followed the link to the paper they cite for a general increase in incidence in top cancers combined in Gen X by the time they reach 60.

> Some portion of these increases can be attributed to rising obesity rates19 and increasingly sedentary lifestyles. 20-23 Another portion might be explained by changes in cancer registry policies and International Statistical Classification of Diseases and Related Health Problems, 10th Revision (World Health Organization) classifications, 24 leading to inclusion of relatively indolent lesions in more recent periods that might not have been diagnosed as cancer in earlier periods. Furthermore, radiologic diagnoses have become more common following widespread deployment of sophisticated medical imaging technologies, 25 especially for thyroid 26,27 and kidney 28,29 cancers. We chose not to exclude any leading cancer site from our summaries because our granular estimates are freely available (eFigures 15-17 in Supplement 1).

https://scholar.google.com/scholar?cluster=51200100901400413...