People are certainly that unlucky to get cancer more than once but I think it's highly unlikely cancer you had 40 years ag would cone back. Once bitten twice shy, I guess. Hang in there and I wish you smooth sailing with no cancer. 

I have had cancer twice in the space of 3 years......still got it in fact, it is now stage 4.  My eldest sister has also had it twice.  Some people get cancer once and luckily it never comes back, whereas other folks get it 2, 3 or more times, and even luckier are those who never get the big C.  You can spend your life thinking 'what if' or you can get on with living.  There are a million 'what ifs' in this world.  What if I cross the road and get hit by a bus?  What if I go for a walk and get hit by a bolt of lightening?  What if I go on a cruise and the ship sinks?  Perhaps I am a bit odd, but I have accepted that I am not going to reach old age, and I am enjoying the time I have got left with my husband.  Violet.