Warning: not an expert. Someone smarter/better educated, correct me (or better, tell me I'm right =) Cancer tends to (though not always) correlate with age whe

Warning: not an expert. Someone smarter/better educated, correct me (or better, tell me I'm right =) Cancer tends to (though not always) correlate with age when you break it up by type of cancer. For example, children don't get prostate cancer or lung cancer all that often. Similarly, Retinoblastoma and other types of cancer are more common amongst children. So, because of that, you have a built-in tendency to control for age and allow the 5-year statistic to be more of a valid comparison. Similarly, you can calculate 5 year survival rates for any set of subgroups you want – break it up by age, race, gender, co-morbidity or even cancer variant (many of those are frequently done) and then compare. At some point (usually in pretty quickly) the 5 year survival rate is a meaningful comparison... Also, to be honest/in my opinion, 5 years is a meaningful number for the lived experience. You can imagine doing a lot in five years vs, say, 6 months – so for that reason, it's a useful metric for generally understanding "what chance do I have at having more life to truly live?"