Understanding ductal carcinoma in situ
For the 62,000 women who will be diagnosed with ductal carcinoma in situ (DCIS) this year, the good news is far more important than the bad. While cancer is never a picnic, DCIS is the earliest detectable form of the disease. Some news that sounds “bad” — for instance, that the incidence of DCIS is increasing faster than that of any other type of breast cancer — is encouraging news. It means that more breast cancers are being detected early, while they can be nipped in the bud. Today, with standard treatment, 10-year survival rates for DCIS are approaching 100%, and the treatment is usually not too difficult to tolerate.
What is DCIS?
The name says a lot about the disease. “Ductal” refers to the site of origin, the tiny ducts that form a network connecting the milk-producing structures called lobules. “Carcinoma” indicates a tumor arising in the epithelium, or lining, of the ducts. “In situ” delivers the good news that the tumor is confined to its place of origin; it hasn’t invaded the surrounding tissue or metastasized to other body tissues.
The diagnosis of DCIS describes a cluster of cells captured in the process of evolving from normal tissue to breast cancer. The journey is thought to begin with a series of genetic changes in breast cells. At first, these changes stimulate cell growth, resulting in ductal hyperplasia (an overabundance of normal cells), which may begin to fill the duct. Then the cells become distorted and look abnormal under a microscope. At this second stage of change, called atypical ductal hyperplasia, the cells’ capacity for growth is further increased. DCIS proper is a third step in the process, in which a cluster of abnormal cells has filled the duct but hasn’t broken through its walls. If it does breach the walls, it’s called invasive breast cancer.
Carcinogenesis, the process by which cancer arises, may not take place precisely in these orderly steps. However, pathologists have developed these classifications as indicators of the progression of the disease.
Like other types of cancer, DCIS is usually diagnosed by a team of medical professionals (including radiologists, surgeons, and pathologists), using the following techniques:
Mammography. In a sense, increased use of mammography is responsible for the increase in DCIS, because it has increased detection. Confined to the ducts, DCIS tumors are often too small to cause symptoms or to be felt on a breast exam. DCIS is likely to be identified during an annual mammogram that reveals tiny calcium deposits — microcalcifications — which appear as lines or clusters on an x-ray image and are sometimes associated with cancer.
Magnetic resonance imaging (MRI) is now increasingly used in breast imaging, but it hasn’t yet been found significantly better than mammography in screening for DCIS.
Biopsy. Once DCIS is suspected, a biopsy is needed to determine whether cancer is actually present and, if so, the extent of the disease.
Pathology. Pathologists examine the biopsy sample to determine how far the tissue has strayed from normal breast tissue. They look at the structure and arrangement of the cells under a microscope and may test the sample to determine the presence of receptors for estrogen and progesterone or abnormalities in genes associated with cancer.
By considering the features and growth pattern of the cells, they will characterize the disease as low grade, intermediate grade, or high grade — a classification that reflects how different the tumor cells look from normal cells and how quickly the tumor is likely to grow.
Until the 1980s, DCIS was routinely treated in the same way as most invasive cancers — with mastectomy. That situation began to change after a large ongoing study, the National Surgical Adjuvant Breast and Bowel Project (NSABP), reported in 1983 that women with small invasive tumors who underwent lumpectomy followed by radiation were just as likely to survive as the women who underwent mastectomy. Physicians naturally assumed that the same approach could also work for patients with DCIS, and that assumption has been confirmed by large studies.
Today, the results of mammography and biopsy determine the choice between mastectomy and lumpectomy. DCIS is never an emergency, so you can take a few weeks to weigh your options, which include the following:
Breast-conserving surgery (lumpectomy) is often recommended when DCIS is limited to one site and the tumor can be removed with a clear margin.
Radiation therapy is recommended for all women who have had breast-conserving surgery, because it reduces the chance of recurrence after surgery from 30% to 15%. The standard procedure is full-breast radiation administered in a hospital or center five days a week for five to eight weeks.
Tamoxifen (Nolvadex) may further reduce the recurrence rate. In a randomized controlled NSABP study reported in 1999, women who received tamoxifen after surgery and radiation for DCIS were only half as likely to have a recurrence within five years, compared with similarly treated women who got a placebo.
Mastectomy is associated with a 10-year disease-free survival rate of 98%. It’s usually reserved for women who have DCIS in more than one part of the breast or in cases where removing the tumor and a margin of healthy tissue around it would require a disfiguringly large incision. Mastectomy is also recommended for women who have a recurrence of DCIS or invasive cancer at the same site. Some women may choose mastectomy because they want to avoid undergoing radiation, or because they want to reduce their risk of recurrence to the lowest level possible.
Because the risk of metastasis is so low, lymph node biopsy is not required for diagnosing DCIS, and adjuvant chemotherapy is not necessary in treating it.
The good news about DCIS
DCIS is sometimes classified as Stage 0 of breast cancer, the earliest stage of the disease. The question for women with this diagnosis is not “Will I live?” but “How much treatment will I need?” One of the biggest risks today is overtreatment. That, too, is changing, as researchers get better at distinguishing the types of tumors that can be subdued without extensive surgery or radiation. DCIS is one cancer that can truly be considered curable.
November 2008 update
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