Causes of Pelvic Cancer

Pelvic cancers are an important health concern for women. The three places in the female pelvis where cancers frequently occur are the cervix, the ovaries and the lining of the uterus, which is known as the endometrium. There are unique causes for each of these cancers. It’s important to remember that when discussing the “cause” of any form of cancer, what’s really at issue is risk, not certainty. Various risk factors may increase the chance of developing a certain type of cancer, and so it is wise to avoid them if possible. However, if cancer does occur, it does not follow that the disease would have been prevented if these risk factors had been avoided.

Cervical Cancer

The major cause of cervical cancer is exposure to certain strains of human papilloma virus (HPV). The virus infects the cells on the surface of the cervix and alters their DNA, making cancer more likely. HPV DNA has been detected in 95% of cervical cancers. HPV is transmitted sexually, so some of the risk factors for cervical cancer are similar to those for any STD: early age at first intercourse, multiple sex partners and male partners with a history of multiple partners. HPV exposure is not the only factor in cervical cancer, however, since many women are infected but relatively few develop cervical cancer. Smoking, exposure to oral contraceptives, other genital infections and decreased immune function make it more likely that exposure to HPV will lead to cancer. A vaccine against the strains of HPV most associated with cervical cancer has recently been developed. If vaccination of young women before they begin sexual activity becomes common, the incidence of cervical cancer should greatly decrease.

Endometrial Cancer

Fibroids are a common benign tumor of the muscles of the uterus, and there are some extremely rare malignant tumors that can also occur in the muscles. However, the overwhelming majority of uterine cancer cases arise in the endometrium. The endometrium grows in response to the hormone estrogen and is shed in response to the hormone progesterone, as part of the normal menstrual cycle. Endometrial cancer is caused by increased exposure to estrogen, particularly in the absence of progesterone. So, the risk factors for endometrial cancer are things which increase lifetime estrogen exposure, including early onset of menstruation, late menopause, obesity, and certain types of medication, like the cancer drug tamoxifen. Obesity increases estrogen exposure because adipose tissue can produce significant amounts of estrogen, particularly in postmenopausal women. In premenopausal women, obesity can lead to polycystic ovary syndrome, which decreases progesterone exposure by preventing ovulation. Oral contraceptives have not been found to be a risk factor, probably because they contain either progesterone only or estrogen combined with progesterone.

Ovarian Cancer

The risk factors for ovarian cancer are much less clear then those for cervical and endometrial cancer. Ovarian cancer is less common in women who have carried multiple pregnancies to term, and more common in women who have never been pregnant or have had frequent miscarriages, although the reasons for these associations are not well understood. Oral contraceptive use also decreases the risk of developing ovarian cancer. As in all cancers, genetic factors play a significant role. The BRCA1 and BRCA2 genes, best known for their role in breast cancer, significantly increase the risk of developing ovarian cancer, although one or both of them is present in only 5% of ovarian cancer cases. Additional genetic links to ovarian cancer will probably be discovered in the future, as research in this area continues.

About this Author

Dr. Christopher Miller specializes in metabolic disease and reproductive endocrinology. He is a graduate of Claremont McKenna College and Drexel University College of Medicine in Philadelphia and has worked for several years in academic medical research. Writing for publication since 1995, he has had articles featured in “Medical Care,” “Preventive Medicine” and “Medical Decision Making.”