Why so many people all at once?

These past two weeks in the news there have been several high profile people who's cancers have returned with a vengeance. Tony Snow, the White House Press Secretary and Elizabeth Edwards, wife of presidential candidate John Edwards to name two. Both of their cancers have spread to other organs in their bodies and the prospects do not look so promising. Taken alone this seems just like something that could happen any time. It seems odd to be because I also know several other instances in the last 30 days or so of people with cancer showing up or returning with a vengeance. My mother's good friend had ovarian cancer. She had been doing really well. I found out last week that it was back and she's in intensive care on a feeding tube and not likely to make it. Another friend told me her good friend's child wasn't feeling well, went to the doctor, found out she had Leukemia and died the next week. A friend from work's Dad's cancer spread to his brain recently and his prospects are not good. Another friend's mother was diagnosed with cancer in several organs and is undergoing rigorous chemo treatments. Maybe this isn't out of the ordinary, it just seems odd to me that I go for long periods of time without anyone I know mentioning cancer and then all these people at once. It just seems odd. Maybe its just my age and the fact that as you get older you have the possibility of knowing more people with the possibility of getting cancer because they are older. Anyway, it sure seems like a bad streak for all these people. I wonder if they have anything in common.