Breast cancer that has not broken out of the ducts and lobules in your breast is called carcinoma in situ. There are two kinds:
Ductal carcinoma in situ (DCIS) - begins in the lining of your ducts. It is thought to be an early form of invasive breast cancer. DCIS is highly curable. Removing it prevents invasive breast cancer.
Lobular carcinoma in situ (LCIS) - begins in the lining of your lobules. LCIS seems to be an indicator for an increased risk of getting invasive breast cancer. The role of early treatment is less clear for LCIS.
With the increasing use of screening mammography, these cancers are more frequently diagnosed. They now make up 15 percent to 20 percent of all breast cancers.
Ductal carcinoma in situ (DCIS) is the earliest possible clinical diagnosis of breast cancer. In fact, it is such an early form of breast cancer that it is also referred to as stage 0. DCIS is frequently diagnosed when a screening mammogram picks up microcalcifications (specks of calcium) in your breast. Women rarely suspect that they have breast cancer with this stage because most of the time you cannot feel a lump.
DCIS is a kind of precancerous or early growth of abnormal cells in the ducts of your breast. Before mammography was available, DCIS was a very uncommon finding in women, and little attention was given to its treatment. This is because DCIS can be cured almost 100 percent of the time by a mastectomy. But with the increased use of screening mammography, women are more likely to have cancer diagnosed at an earlier stage. So the number of women in whom DCIS is diagnosed is increasing.
If not treated, DCIS can turn into invasive breast cancer (stage I or higher). On average, if this happens, it happens after about 5 to 8 years. If DCIS is untreated, about 30 percent of women will get invasive breast cancer an average of 10 years later.
Treatment of DCIS
The tissue from your DCIS biopsy will be tested to see whether it is estrogen-receptor positive (ER-positive).
Grade
DCIS has three grades. The grade of cancerous tissue is determined in laboratory tests performed by a pathologist, who examines the appearance of the cells under a microscope. Knowing the grade of the cancerous tissue will help your health care provider suggest treatment options. The three grades are:
Grade I: low-grade. These cells look similar to normal cells and tend to grow slowly. Low-grade DCIS is also referred to as "well-differentiated," meaning that the cancer cells look like normal cells.
Grade II: moderate-grade. This grade is in between low and high grade and these cells also tend to grow slowly.
Grade III: high-grade. These cells are more likely to grow faster and become invasive. This type of DCIS is also called comedo or comedo necrosis. The cells are referred to as "poorly differentiated," meaning that they do not look at all like normal cells.
Surgery
Because of advances in cancer detection and treatment, there are many treatment options for women with DCIS. In the past, surgical removal of the affected breast—called a mastectomy—was recommended. This treatment results in cure rates of 98 percent to 99 percent. Rarely, the cancer recurs (comes back) in your armpit (axilla), in your other breast, or in some other part of your body.
Because of this success, doctors recently began using another type of surgery—called breast-conserving surgery—to treat DCIS that removes only the part of the breast that has cancer cells. This type of surgery may involve a partial mastectomy (removal of the cancer, some healthy breast tissue, and sometimes the area lymph nodes). Or it may involve a lumpectomy (removal of the cancer and a margin of normal tissue around the cancer).
DCIS is unlikely to have spread to your axillary lymph nodes, so a procedure called axillary lymph node dissection is not routinely done. Most studies indicate that only 1.4 percent of women with DCIS who have no evidence of spread of cancer cells to the ductal membrane (called microinvasion) have cancer in their axillary lymph nodes.
Women with extensive DCIS, larger tumors, and high-grade comedo type of cancer are more likely to be at risk for cancer spread to the lymph nodes. If you are one of these women, your doctor may suggest that you have an axillary lymph node dissection or a sentinel lymph node biopsy at the time of your surgery.
Types of Surgery
Total mastectomy - This involves complete removal of your breast. It is associated with a cure rate of nearly 98 percent to 99 percent. If you have a total mastectomy, you do not need any more treatment to that breast.
Breast-conserving surgery - This has been used successfully to treat DCIS in the past 30 years. A current goal of treatment for women with DCIS is breast conservation with the best possible cosmetic result and the lowest possible risk of the cancer becoming invasive or recurring.
Current clinical studies suggest that women who have breast-conserving surgery may have a slightly higher risk of cancer recurrence than women who have a mastectomy.
When breast-conserving surgery is performed, a margin of normal-appearing tissue around the cancer is also removed (this is called the surgical margin). After breast-conserving surgery, recurrence rates appear to be related to the surgical margin. Doctors agree that adequate surgery includes a margin of 10 millimeters or greater between DCIS and normal tissue.
Breast-conserving surgery is advised for the majority of women with a small (2-centimeter to 3-centimeter) cancer with margins of 10 millimeters or greater or cancer that has an intermediate nuclear grade. Mastectomy is reserved for the minority of women with a large cancer or multiple areas of DCIS in their breast, or women who cannot have radiation therapy.
For some women with small cancers and wide surgical margins, this surgery alone is probably curative. But in general, most women having breast-conserving surgery will probably be advised to have radiation therapy, with or without antihormonal therapy, to lower their risk of recurrence as much as possible.
Radiation Therapy
If you have DCIS and have a mastectomy, you do not need radiation therapy. But it is clear that if you have a lumpectomy, having radiation therapy afterward decreases your risk of recurrence. In one study, 818 women with DCIS and negative surgical margins (meaning no cancer was detected at the edge of the tissue taken out) received radiation therapy or no further therapy after a lumpectomy. Eight years later, invasive cancer was found in 3.9 percent of women treated with radiation compared with 13.4 percent of women not treated with radiation.
Antihormonal Therapy
The hormone estrogen makes some breast cancers grow. Estrogen is a female hormone made mainly by your ovaries. Many organs in your body have cells that respond to estrogen. Cells in your breast, uterus, and other female organs have areas on them that bind estrogen. These areas are called estrogen receptors.
When estrogen binds to the receptors, the cells are stimulated to grow. When cells that have estrogen receptors become cancerous, estrogen can make them grow faster. So the aim of antihormonal therapy is to prevent the cancer cells from being exposed to estrogen.
Removal of the main source of estrogen, your ovaries, is one effective way to stop estrogen production. This is commonly done in many countries in women with ER-positive breast cancer. Chemotherapy can also stop your ovaries from releasing estrogen.
Another approach is to use drugs that have a similar effect without removing your ovaries. The drug most commonly used for antihormonal therapy of breast cancer for many years was tamoxifen, which works by blocking estrogen receptors. This prevents the estrogen from stimulating the growth of breast cancer cells.
Studies suggest that the combination of surgery, radiation therapy, and tamoxifen are more effective at preventing invasive breast cancer in women with DCIS than surgery and radiation therapy without tamoxifen. However, the addition of tamoxifen does not increase overall survival.
Tamoxifen has possible side effects, including uterine wall thickening and the risk of endometrial (uterine) cancer and the development of blood clots in leg veins. So you should discuss the risks and benefits of tamoxifen with your health care provider. Women who take tamoxifen should be monitored by having regular gynecologic examinations.
Today, many women with breast cancer are treated with newer antihormonal-hormonal therapies called aromatase inhibitors, which are approved by the U.S. Food and Drug Administration for the treatment of ER-positive breast cancer in postmenopausal women. They are: Femara® (letrozole), Arimidex® (anastrazole), and Aromasin® (exemestane).
These drugs act by reducing the amount of estrogen available to the tumor cells. Aromatase inhibitors do not have the same side effects as tamoxifen, but all drugs have some side effects. The main side effect of aromatase inhibitors is bone loss and joint discomfort. Aromatase inhibitors are even more successful than tamoxifen in preventing recurrences of invasive breast cancer, but they are not approved for the treatment of DCIS.
Strategies to Improve Treatment
The progress that has been made in treating DCIS has resulted from doctor and patient participation in clinical trials. Future progress in the treatment of DCIS will result from continued participation in appropriate studies.
An area of active study to improve the treatment of DCIS is identifying women who can be cured with surgery alone by looking at the characteristics of the DCIS. Improvements in this area could spare the majority of women the need for radiation therapy.
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