A couple of things:
One of the posters is correct that our collective lifespan has increased over the last few decades. Older people are more likely to get cancer. We have also become very good at treating/preventing other causes of premature death, like cardiovascular disease, accidents, and so on. Not dying of other stuff...more cancer.
The second factor is possibly temporary in Canada. In the early 90s, the governments radically dropped the taxes on cigarettes in an effort to curb contraband smuggling. The result was an explosion in youth smoking rates, particularly young women. Taxes were ultimately increased again, but not before an entire cohort of people became smokers. It's been roughly 20-25 years, about the right time lag for smoking to cause the cancers it does.
The other increases in cancer are potentially artifact because of major increases in screening. Screening invariably increases the incidence rates, because it introduces length bias and overdiagnosis bias. Those of you fancying yourself as pre-meds should learn all these terms, but suffice it to say that screening will detect cancers that: 1) are slower-growing and less aggressive, or 2) would have never become a life-threatening problem...the patient would have died with the cancer, not from the cancer.
The textbook example of this is prostate cancer detection with the PSA test. This single blood test has led to an explosion in the incidence of prostate cancer, but death rates in screened prostate cancer patients haven't changed all that much. It means we are detecting and treating a whole lot of cancer we might not have needed to bother with. There is a similar controversy around the usefulness of screening mammography, but it's nothing as compared with the infighting over PSA.
