She can not have babies if they removed all or part of any essential organs needed for gestating a baby.
For instance if she had cervical cancer and had her cervix removed she has no ability to carry a fetus to term.
Otherwise I see no reason why she could not have a child.
I have heard of women who have carried and birthed children while currently battling cancer (the tumor is found afterwards) and can even be treated for various cancers during pregnancy.
http://news.yahoo.com/s/hsn/20060624/hl_hsn/breastcancertreatmentsafeduringpregnancy (article about treatment of breast cancer during pregnancy).
I remember a woman on "A Baby Story" who was being treated for breast cancer while pregnant.