DFCI care team answers questions about DCIS
What is DCIS?
Ductal Carcinoma in situ (DCIS) is the most common type of non-invasive cancer of the breast. It is a condition in which cancer cells have developed inside the milk ducts of the breast, but they have not escaped into the surrounding tissue; at this stage, the cancer is in situ, or "in place," and is not dangerous. DCIS is such an early form of cancer that some doctors refer to it as "pre-cancer," though others disagree. DCIS accounts for nearly 20 to 25 percent of all diagnoses of breast cancer. Some proportion of DCIS lesions will eventually extend beyond the milk ducts and become invasive cancers. More than 47,000 cases of DCIS have been diagnosed annually in recent years, in addition to some 200,000 cases of invasive breast cancer.
How is DCIS diagnosed?
The first sign of DCIS is usually detected on a routine mammogram; prior to the wide use of mammography, the condition was rarely diagnosed until tumors became large enough to be felt. DCIS often appears on a mammogram as tiny specks of calcium, called microcalcifications. The diagnosis is confirmed with a biopsy in which a small sample of cells is removed and studied under a microscope.
What are the treatment options for DCIS?
Many women with DCIS can be treated with a lumpectomy (surgery to remove the lesion). This is called "breast-conserving" treatment. It is recommended for women with small DCIS lesions and leaves a margin of cancer-free tissue on all sides of the DCIS. Following lumpectomy, most women need to undergo six to seven weeks of radiation therapy to destroy any remaining cancer cells. In other cases, the DCIS lesion is large, or there are several of them in the breast. At this stage, it's impossible for the surgeon to achieve clear margins of sufficient size of cancer-free tissue surrounding the lesion. For these patients, a mastectomy — removal of the entire breast — is the safest strategy to ensure all the cancer has been eliminated.
Doctors emphasize that a diagnosis of DCIS should not cause women to rush into one treatment or another. There is plenty of time to become familiar with the disease and with the various treatment options, and arrive at a well-reasoned decision.
What is the role of tamoxifen in treatment for DCIS?
Physicians don't prescribe chemotherapy for women with DCIS, but patients may be offered the estrogen-blocking drug tamoxifen as an additional protection against cancer recurrence. Tamoxifen, long used as part of treatment for breast cancer and to prevent the disease in women who are at high risk, was approved in 2000 by the U.S. Food and Drug Administration for women following surgery for DCIS.
In clinical trials, tamoxifen reduced the cancer recurrence rate from 13 percent to about 8 percent in women who had had lumpectomy and radiation as their DCIS treatment. That benefit must be weighed against the side effects of tamoxifen, which include hot flashes and weight gain and, rarely, the development of blood clots or endometrial cancer.
What is my outlook if I have been diagnosed with DCIS?
Because DCIS by definition has not spread or invaded nearby tissues, it is highly curable as long as the patient undergoes an accepted form of treatment. If not treated, many DCIS lesions will, over time, become invasive cancers that threaten to spread and become dangerous; physicians cannot predict, however, which cases of DCIS will turn into invasive tumors.
