What is Breast Cancer?
Before discussing, it’s important to be familiar with the anatomy of the breast. The normal breast consists of milk-producing glands that are connected to the surface of the skin at the nipple by narrow ducts. The glands and ducts are supported by connective tissue made up of fat and fibrous material. Blood vessels, nerves, and lymphatic channels to the lymph nodes make up most of the rest of the breast tissue. This breast anatomy sits under the skin and on top of the chest muscles.
As in all forms of cancer, the abnormal tissue that makes up breast cancer is the patient’s own cells that have multiplied uncontrollably. Those cells may also travel to locations in the body where they are not normally found. When that happens, the cancer is called metastatic.
Breast cancer develops in the breast tissue, primarily in the milk ducts (ductal carcinoma) or glands (lobular carcinoma). The cancer is still called and treated as breast cancer even if it is first discovered after the cells have traveled to other areas of the body. In those cases, the cancer is referred to as metastatic or advanced cancer.
It usually begins with the formation of a small, confined tumor (lump), or as calcium deposits (microcalcifications) and then spreads through channels within the breast to the lymph nodes or through the blood stream to other organs. The tumor may grow and invade tissue around the breast, such as the skin or chest wall. Different types of cancer grow and spread at different rates — some take years to spread beyond the breast while others grow and spread quickly.
Some lumps are benign (not cancerous), however some of these can be premalignant. The only safe way to distinguish between a benign lump and cancer is to have the tissue examined by a doctor through a biopsy.
Men can get this disease, too, but they account for just one percent of all cases. Among women, it is the most common cancer and the second leading cause of cancer deaths after lung cancer.
If eight women were to live to be at least 85, one of them would be expected to develop the disease at some point during her life. Two-thirds of women with cancer are over 50, and most of the rest are between 39 and 49.
Fortunately, it is very treatable if detected early. Localized tumors can usually be treated successfully before the cancer spreads; and in nine out of 10 cases, the woman will live at least another five years. However, late recurrences of cancer are common.
Once the cancer begins to spread, treatment becomes difficult, although treatment can often control the disease for years. Improved screening procedures and treatment options mean about 8 out of 10 women will survive at least 10 years after initial diagnosis.
What Causes Breast Cancer?
Although the precise causes are unclear, we know what the main risk factors are. Still, most women considered at high risk for cancer do not get it. On the other hand, 75% of women who develop have no known risk factors. Among the most significant factors are advancing age and family history. Risk increases slightly for a woman who has certain benign breast lumps and increases significantly for a woman who has previously had or endometrial, ovarian, or colon cancer.
A woman whose mother, sister, or daughter has had breast cancer is two to three times more likely to develop the disease, particularly if more than one first-degree relative has been affected. This is especially true if the cancer developed in the woman while she was premenopausal, or if the cancer developed in both breasts.
Researchers have now identified two genes responsible for some instances of familial breast cancer — BRCA1 and BRCA2. About one woman in 200 carries one of these genes. Having a BRCA1 or BRCA2 gene predisposes a woman to breast cancer, and while it does not ensure that she will get breast cancer, her lifetime risk is 45% – 80%. These genes also predispose to ovarian cancer and are associated with pancreas cancer, melanoma, and male breast cancer (BRCA2).
Because of these risks, prevention strategies and screening guidelines for those with the BRCA genes are more aggressive. There are other genes that have been identified as increasing the risk of breast cancer, including the PTEN gene, the ATM gene, the TP53 gene, and the CHEK2 gene. However, these genes carry a lower risk for breast cancer development than the BRCA genes.
Generally, women over 50 are more likely to get breast cancer than younger women, and African-American women are more likely than Caucasians to get breast cancer before menopause.
A link between cancer and hormones is clear. Researchers think that the greater a woman’s exposure to the hormone estrogen, the more susceptible Estrogen tells cells to divide; the more the cells divide, the more likely they are to be abnormal in some way, potentially becoming cancerous.
A woman’s exposure to estrogen and progesterone rises and falls during her lifetime. This is influenced by the age she starts menstruating (menarche) and stops menstruating (menopause), the average length of her menstrual cycle, and her age at first childbirth. A woman’s risk is increased if she starts menstruating before age 12 (less than 2 times the risk), has her first child after 30, stops menstruating after 55, or does not breast feed.
Current information about the effect of birth control pills and breast cancer risk is mixed. Some studies have found that the hormones in birth control pills probably do not increase cancer risk or protect . However other studies suggest that the risk of breast cancer is increased in women who have taken birth control pills recently, regardless of how long she has taken them.
Some studies suggest that the use of hormone replacement therapy with combined estrogen and progesterone containing compounds increases the risk of developing cancers. They also show, after a 7 year follow up, that the use of estrogens alone does not increase or decrease the risk of breast cancer development. Their use may, though, increase the risk of clotting.
High doses of radiation, such as with nuclear exposure, or therapeutic radiation, such as used for Hodgkin lymphoma, are a factor for cancer development after15-20 years. Mammography poses almost no risk of breast cancer development.
The link between diet and cancer has been debated. Obesity is a noteworthy risk factor, predominately in postmenopausal women, because obesity alters a woman’s estrogen metabolism. Drinking alcohol regularly — particularly more than one drink a day — also increases the risk of breast cancer. Many studies have shown that women whose diets are high in fat, either from red meat or high-fat dairy products, are more likely to get the disease. Researchers suspect that if a woman lowers her daily calories from fat — to less than 20-30 percent — her diet may help protect her from developing breast cancer.
What Are the Symptoms of Breast Cancer?
The signs and symptoms of breast cancer include:
- A lump or thickening in or near the breast or in the underarm that persists through the menstrual cycle
- A mass or lump, which may feel as small as a pea
- A change in the size, shape, or contour of the breast
- A blood-stained or clear fluid discharge from the nipple
- A change in the feel or appearance of the skin on the breast or nipple (dimpled, puckered, scaly, or inflamed)
- Redness of the skin on the breast or nipple
- An area that is distinctly different from any other area on either breast
- A marble-like hardened area under the skin
These changes may be found during a breast self-exam.
Medical organizations don’t agree on the recommendation for breast self-exams, which is an option for women starting in their 20s. Doctors should discuss the benefits and limitations of breast self-exams with their patients.
Hormone Receptor-Positive Breast Cancer
About 80% of all breast cancers are “ER-positive.” That means the cancer cells grow in response to the hormone estrogen. About 65% of these are also “PR-positive.” They grow in response to another hormone, progesterone.
If your breast cancer has a significant number of receptors for either estrogen or progesterone, it’s considered hormone-receptor positive.
Tumors that are ER/PR-positive are much more likely to respond to hormone therapy than tumors that are ER/PR-negative.
You may have hormone therapy after surgery, chemotherapy, and radiation are finished. These treatments can help prevent a return of the disease by blocking the effects of estrogen. They do this in one of several ways.
The medication tamoxifen (Nolvadex, Soltamox) helps stop cancer from coming back by blocking hormone receptors, preventing hormones from binding to them. It’s sometimes taken for up to 5 years after initial treatment ..
A class of medicines called aromatase inhibitors actually stops estrogen production. These include anastrozole (Arimidex), exemestane(Aromasin), and letrozole (Femara). They’re only used in women who’ve already gone through menopause.
CDK 4/6 inhibitors palbociclib (Ibrance) and ribociclib (Kisqali) are sometimes used with aromatase inhibitors in women with certain types of advanced breast cancer who have gone through menopause. Abemaciclib (Verzenio) and palbociclib can sometimes be used with the hormone therapy fulvestrant (Faslodex).
HER2-Positive Breast Cancer
In about 20% of breast cancers, the cells make too much of a protein known as HER2. These cancers tend to be aggressive and fast-growing.
For women with HER2-positive breast cancers, the drug trastuzumab(Herceptin) has been shown to dramatically reduce the risk of the cancer coming back. It‘s standard treatment to give this medication along with chemotherapy after surgery to people with breast cancer that’s spread to other areas. It can also be used for early-stage breast cancer. But there is a small but real risk of heart damage and possible lung damage. Scientists are still studying how long women should take this medication for the greatest benefit.
Another drug, lapatinib (Tykerb), is often given if trastuzumab doesn’t help. Ado-trastuzumab emtansine (Kadcyla) can be given after trastuzumab and a class of chemotherapy drugs called taxanes, which are commonly used to treat breast cancer.
Pertuzumab (Perjeta) can be used with trastuzumab and other chemotherapy medicines to treat advanced breast cancer. This combination can also be given before surgery to treat early breast cancer. In one study, the combination of the two drugs it was shown to extend life.
Triple-Negative Breast Cancer
Some breast cancers — between 10% and 20% — are known as “triple negative” because they don’t have estrogen and progesterone receptors and don’t overexpress the HER2 protein. Many breast cancers associated with the gene BRCA1 are triple negative.
These cancers generally respond well to chemotherapy given after surgery. But the cancer tends to come back. So far, no targeted therapies have been developed to help prevent cancer returning in women with triple-negative breast cancer. Cancer experts are studying several promising strategies aimed at triple-negative breast cancer.
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