Talcum powder is made of talc. A mineral which contains mainly the elements magnesium, silicon, and oxygen.
I have a very hard time believing talc can cause cancer. If it did wouldn't it be a cancer in the area where it made contact and not a part of the body well away from the contact? Talcum powder is used as an anticaking agent in table salt.
A wiki article indicates there are 1200 lawsuits pending for this issue.
The only risk I found was that talc is mined from areas where asbestos is found. Proper mining techniques prevent contamination and testing by the Govt has shown zero asbestos in samples of talc. again according to wiki one of the studies on whether it was safe, published in 1993, was a US National Toxicology Program report, which found that cosmetic grade talc containing no asbestos-like fibres was correlated with tumor formation in rats forced to inhale talc for 6 hours a day, five days a week over at least 113 weeks
This is nothing more than a shake down of deep pockets.