In terms of cancer (or at least the one I had) five years is a big deal as it marks a major transition point. When I saw my endo doc this spring I confirmed that time frame, and asked what day I should count from, since the summer of 2009 had a lot of events surrounding this issue. She told me that traditionally everything counts from diagnosis.
So for the past several years, if you had asked for some reason, I would have told you, “I have cancer that has been fully in remission for X amount of time”.
But as of Monday I get to tell you, “I had cancer”.
Nothing has changed, but words matter.