Early Pregnancy Lowers Breast Cancer Risk | Dr. Kathleen T ...

A full-term pregnancy produces permanent genetic and biologic changes in the cells in the breast. ?Should a first full-term pregnancy occur prior to age twenty, these permanent changes produce a life-time reduction in the risk for estrogen-positive breast cancer, the most common form of the disease (80%.)

How does early pregnancy lower the risk for breast cancer? ?Let?s begin with a discussion of the normal architecture in the breast and then move on to how pregnancy changes all that.

The breast is comprised of several different types of cells: ?lobular cells that produce milk, ductal cells that carry the milk to the nipple, and fat cells that round out everything else. ?In the adult breast there are three types of lobular cells: ?type 1,2 and 3. ?In the lactating breast there is an additional lobular cell, type 4. ?Then once a woman goes through menopause, all the lobular cells become type 1.

Whereas all post-menopausal women have lobular type 1 cells, women who have had early pregnancy appear to have genetically altered type 1 cells that are resistant to malignant transformation. ?All post-menopausal women appear to have similar lobular type 1 cells when you look at them under the microscope, but when you take a closer look at the genes contained in these lobular type 1 cells, there are significant differences between those who have had early pregnancies and those who have not. These genetic differences become biologic differences that translate into a reduced risk for breast cancer for the remainder of a woman?s life. In fact, women who have a first full-term pregnancy before the age of twenty have one half the risk of developing estrogen-positive breast cancer compared to women whose first pregnancies occur after the age of thirty, or not at all.

Pregnancy alters the genetic profile of type 1 lobular cells, making them resistant to malignant transformation. ?Researchers are not certain what, exactly, is responsible for the genetic changes that protect lobular type 1 cells from the changes that lead to cancer, but at least two hormones associated with pregnancy appear to play a role in lowering the risk for breast cancer.

The first of these hormones is estriol, which is produced in small quantities by the ovaries in the non-pregnant menstruating female, but which is produced at 1000 times normal levels in the final three months of pregnancy. ?Estriol appears to alter the genetic profile of normal breast cells, making them more stable and resistant to malignant transformation.

The other hormone that may play a role in protecting lobular type 1 cells is HCG, human chorionic gonadatropin, also produced in very high quantities during pregnancy. ?Scientists at Fox Chase Cancer Center studied the role of HCG and breast cancer by taking rats with a normally high rate of breast cancer and separating them into four groups. ?The first group was the control group; these rats were just observed over a period of months. ?The next three groups were given increasing exposure to HCG: for 5, 10, and 15 days each. ?The results were dramatic and provocative.

The first group of rats, those that were merely observed had a 91% incidence of breast cancer.

The rats that received 5 days of HCG had a 71% incidence of breast cancer.

The rats that received 10 days of HCG had a 57% incidence of breast cancer.

And the rats that received 15 days of HCG had a 15% incidence of breast cancer.

It would appear from this study that HCG significantly reduces the risk for breast cancer, in rats. ?The next step is to see if HCG might also reduce the risk for breast cancer in women, providing the same beneficial effects as an early full-term pregnancy.

Here?s an excellent bird?s eye view of a discussion that occurred just last year about this subject: ?the discussion occurs among really top of the pyramid breast cancer researchers. ?The good news is that I think we?re getting closer to answering the question this year.

References

Russo J, The protective role of pregnancy in breast cancer. Breast Cancer Res., 2005, 7(3): 131-42

Russo J, The genomic signature of breast cancer prevention, Cancer Res, 2007: 174-131

Russo J, The concept of stem cell in the mammary gland and its implication in morphogenesis, cancer and prevention. Front Biosc 2006 Jan 1; 11: 151-72

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Source: http://breastcancerbydrruddy.com/?p=2674

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