I don't see how this does anything to affect the abortion debate either way.
If you believe - as some people do - that foetuses are not human and that it is all right to abort them because they are not human beings, it wouldn't matter that it increases the risk of cancer. It would then be a woman's right to decide if she wants to risk cancer or not.
If you believe - as yet others do - that foetuses are human and that it is still all right to abort them, then it wouldn't matter, too - and for the same reason.
OTOH, if you believed that abortion is murder and should not be permitted, it would not matter if it causes cancer. Murder is wrong, whether it does the the murderer harm or not.
The problem with abortion is not that is healthy or not. The problem is that it is an issue that is held by at least one side of the debate to concern two entities, a mother and her child.