Well, no, we cannot say that abortion causes cancer. However, there is some evidence which indicates that abortion increases risk of breast cancer. I have linked an article here which describes some of the psychological, social, and medical ill effects of abortion. From the article:
In contrast to full term birth, induced abortion does not have a protective effect. A meta-analysis of 28 published reports on abortion and breast cancer concluded there was an independent 30%-50% increased risk for breast cancer as a result of induced abortion. Higher risks for breast cancer occurred among women with two or more induced abortions compared to women with one induced abortion in seven of ten studies57. Although the evidence is inconsistent, the relative risk of breast cancer conferred by a family history of breast cancer has been found to further increase with the number of induced abortions58.