Q1. I decided at a young age not to have children, and I haven't regretted my choice. I keep reading, though, that women who are childless are at a higher risk for some types of cancer as they get older. Why is this so, and which cancers am I more likely to get? Is there anything I can do about it now? (I'm in my fifties.)

Women who have been pregnant appear to be at a lower risk for breast cancer, endometrial cancer, and ovarian cancer. Women who have had children, particularly if they also breastfed following pregnancy, have a lower risk of breast cancer. This is likely due to the fact that pregnancy and lactation interrupt ovulation for a period of time, and this alteration in the hormonal environment reduces breast-cancer risk somewhat. Similarly, the endometrium — the lining of the uterus — is sensitive to its hormonal environment, and exposing the endometrium to both estrogen and progesterone (as happens during pregnancy or with the use of oral contraceptive pills that contain both estrogen and progestins) is associated with a lower endometrial cancer risk. Finally, women who have used oral contraceptives (birth control pills) have a reduced risk of ovarian cancer, whether they have had children or not. This is likely attributable to the fact that both pregnancy and oral contraceptives decrease the total number of lifetime ovulatory cycles.

Whether they have had children or not, there are many things that women in their fifties should do in terms of appropriate screening for cancer, including undergoing annual mammograms to look for early stage breast cancer, screening colonoscopies every five to ten years, and an annual pelvic examination and Pap smear; and maintaining a normal weight since the excess estrogen of obesity increases the risk of endometrial cancer and possibly breast cancer.

Women who have chosen to take estrogen replacement therapy following menopause should review this decision with their doctors to determine if such treatment remains the right choice. In addition, every woman should be familiar with her family history of cancers and discuss these in detail with her doctor. Some families carry an inherited predisposition to certain cancers. In such families, recommendations for cancer screening and testing may be altered in order to maximize the opportunity for early detection.

Q2. What percentage of myomas become cancerous in the future? When do you recommend surgery to remove a myoma – when its size is more than 6 cm, or by how fast it grows?

— Celia, Washington

When it comes to myomas, neither size nor progression is a definitive indicator of cancer or for surgery. First, a little background information: Myomas, also called fibroids and leiomyomas, are benign (not cancerous) growths that commonly occur in the wall — the smooth muscle portion –– of the uterus. They are typically found in women who are still having periods (premenopausal women) and often will regress after menopause, when there is less estrogen circulating to stimulate them. Leiomyomas may cause no symptoms, in which case they are found incidentally when a woman has a sonogram for some other reason or they are felt on physical examination, or they may cause heavy periods or irregular bleeding, pelvic pain or pressure, and recurrent urinary tract infections.

Most studies suggest that benign leiomyomas do not turn into cancer. Benign leiomyomas can be present in the same uterus that has a leiomyosarcoma (a true cancer of the smooth muscle tissue of the uterus), but the two types most likely grew from separate cells rather than some of the benign leiomyoma cells becoming malignant.

One could ask your question this way: Of all the women whose leiomyomas are bothersome enough or large enough that they elect to have the uterus removed (hysterectomy), what percentage are found to actually have had a leiomyosarcoma (cancer) instead of just a benign leiomyoma? The answer is about 1 to 2 in 1,000. This is true even for women who have a hysterectomy because of a "rapidly growing" fibroid. These numbers are usually quite reassuring to women with leiomyomas who are not having any physical symptoms.

The specifics of how you and your doctor deal with your myoma depend on such things as whether you wish to preserve your fertility and whether you have any symptoms or significant bleeding. You can talk to your doctor about these issues. The answers will help you decide among such choices as observation of the fibroid for now, treatments to change your hormone levels, surgery to try to remove just the fibroid (myomectomy), or surgery to remove the uterus (hysterectomy).

Learn more in the Everyday Health Cancer Center