It is NOT true!! Cancer is not rare at all in India, though certain types of cancer are rare (such as colon cancer). Also, Alzheimer's is getting more and more common - one of my aunts suffered from Alzheimer's before she died.
But Turmeric is a powerful herb - it is a purifier of the blood and it is very good for you. It is best eaten in its raw form, and also does wonders for the skin if you make a paste out of the root and slather it over the face.
It really is an amazing herb but one needs to be careful before making claims about the occurrence of cancer!