Being "grateful" for cancer does rather beg the question of what one's life was like beforehand. Most people would prefer not to have ticked that box at all, and those that have been through it have very different experiences. As we hear ad infinitum, cancer is not one thing and people's experience of it is not one single definable thing either. Some of us have been able to get through with not too much physical or mental damage, perhaps a bit more self knowledge and appreciate years of living that just might never have happened. Personally, I view any variation on the "pain/misery/etc is sent to make us better people" line as insult added to injury!!