Breast cancer: what are the risks?

About 190,000 new cases of invasive breast cancer and 60,000 cases of non-invasive breast cancer will be diagnosed in American women this year. Approximately 2,000 cases of breast cancer will be diagnosed in American men this year.

The number one risk for breast cancer is being a woman over 50. Women under 45 account for about 1-in-8 invasive breast cancers. Women older than 55 account for 2-in-3 invasive breast cancers. The longer we live, the more opportunity for genetic damage.

The risk that a woman will be diagnosed with breast cancer during the next 10 years, starting at the following ages, is as follows:

  • Age 30 . . . . . . 0.44 percent (or 1 in 227)
  • Age 40 . . . . . . 1.47 percent (or 1 in 68)
  • Age 50 . . . . . . 2.38 percent (or 1 in 42)
  • Age 60 . . . . . . 3.56 percent (or 1 in 28)
  • Age 70 . . . . . . 3.82 percent (or 1 in 26)

There are a myriad of other risk factors, many beyond our control.

Genetic mutations, such as those found in BRCA1 and BRCA2, elevate the risk of breast cancer as well as ovarian cancer.

Family history. If you’ve had one first-degree female relative (sister, mother, daughter) diagnosed with breast cancer, your risk of breast cancer doubles. If two first-degree relatives have been diagnosed, your risk is five times average. Sometimes family history is linked to BRCA1 or BRCA2 genes.

Personal history. If you’ve been diagnosed with breast cancer, you’re 3 to 4 times more likely to develop a new cancer in the other breast or a different part of the same breast. If you’ve been diagnosed with atypical hyperplasia or LCIS (lobular carcinoma in situ), your risk of developing breast cancer is elevated. A woman with LCIS is at an elevated risk for the rest of her life.

Early menstrual period, menopause after age 55. The earlier you start your periods (before 12) and/or entering menopause at an older age will slightly increase your risk of breast cancer. The risk may be related to longer lifetime exposure to estrogen and progesterone hormones.

Late or no pregnancyHaving your first pregnancy after age 30 or never having a full-term pregnancy can raise breast cancer risk. Breast cells are  highly active until your first full-term pregnancy. In this active and immature state, your breast cells are very responsive to estrogen and other hormones. Breast-feeding may help to lower your breast cancer risks.

Having dense breasts. Dense breasts can make it more difficult to see tumors on a mammogram. But women with dense breasts are also more likely to get breast cancer.

Being overweight or obese defined as having a BMI (body mass index) above 25, have an increase risk of being diagnosed with breast cancer, especially if the weight is gained after menopause. Being overweight also can increase the risk of breast cancer coming back. This increased risk may be because fat cells make estrogen, and estrogen can make hormone-receptor-positive breast cancers develop and grow.

Combined post-menopausal hormone therapy after menopause for more than five years increases the risk of developing breast cancer.  The hormones  estrogen and progestin, when taken together, have been shown to increase risk.

Taking oral contraceptives (birth control pills). Certain forms of oral contraceptive pills have been found to raise breast cancer risk. The risk decreases over time once the pills are stopped.

Diethylstilbestrol exposure (DES), a drug commonly given to pregnant women from 1940 to 1971 to prevent miscarriage, may slightly increase the risk of developing breast cancer. Women whose mothers took DES during pregnancy may also have a slightly higher risk of breast cancer.

Not being physically active. Exercising regularly at a moderate or intense level for 4 to 7 hours per week reduces breast cancer risk. Exercise helps control blood sugar and limits blood levels of insulin growth factor, a hormone that can affect how breast cells grow and behave.

This is by no means an exhaustive list of risks. Sadly, scientists do not know what triggers most breast cancer, so there are many risk factors but most only elevate the risk slightly. Put several of them together, however, and your risk could be significantly elevated.



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