DCIS (ductal carcinoma in situ) is the most common form of non-invasive breast cancer and is considered stage 0 cancer. While DCIS isn’t considered life threatening, it does increase the risk of developing invasive breast cancer later in life.
DCIS usually is found when a biopsy is done on a suspicious area found by a mammogram. As old cancer cells die off and pile up, tiny specks of calcium (called "calcifications" or "microcalcifications") form within the broken-down cells. The mammogram will show the cancer cells inside the ducts as a cluster of these microcalcifications, which appear either as white specks or as a shadow. Most of the time, you don’t feel DCIS as a lump. If the biopsy results find DCIS, doctors want to remove the whole area of concern to make sure the DCIS has been removed completely. It’s most important to know if there’s any evidence of invasive cancer.
DCIS usually is treated with surgery to remove the cancer – in most cases a lumpectomy even though DCIS doesn’t usually form a lump. After lumpectomy, many women have radiation therapy to the rest of the breast. Radiation reduces the risk of an invasive cancer and also helps reduce the risk of DCIS coming back (recurrence). If the DCIS is hormone-receptor-positive (most are), hormonal therapy also may be recommended after lumpectomy.
Sometimes DCIS is “diffuse” -- meaning that it’s in multiple areas of the breast or there’s one area that occupies much of the breast. Diffuse DCIS can show up with several clusters of calcifications. Other times, the pathology report shows DCIS involving a much larger area of the breast than shown by the mammogram.
A study pulled together the results of treatment on women diagnosed with DCIS. It looked at survival: how many women ultimately die from breast cancer after first being diagnosed with DCIS. Other factors that influenced breast cancer mortality also were analyzed. The results showed that 20 years after a DCIS diagnosis, about 3% of women would die from breast cancer. The risk of dying from breast cancer among all the women who were diagnosed with DCIS was 1.8 times higher than that of the general U.S. population. Women who were diagnosed with DCIS when they were younger than 35 and black women were more likely to die from breast cancer than other women.
The study was published online on Aug. 20, 2015 by JAMA Oncology. Read “Breast Cancer Mortality After a Diagnosis of Ductal Carcinoma In Situ.”
In the study, the researchers looked in the SEER databases to find 108,196 women diagnosed with DCIS between 1988 and 2011. The SEER databases are large registries of cancer cases from sources throughout the United States maintained by the National Institutes of Health. The women ranged in age from 15 to 69 years of age.
The researchers noted:
- the women’s age at diagnosis
- the women’s race/ethnicity
- characteristics of the DCIS
- the type of surgery a woman had (lumpectomy vs. mastectomy)
- any other treatments a woman had (radiation, chemotherapy, hormonal therapy, targeted therapy)
- date of a diagnosis of a second primary breast cancer (if any)
- the women’s cause of death
- the women’s survival time after diagnosis
The women were followed anywhere from 0 to 23.9 years. About half the women were followed for less than 7.5 years and the other half were followed for more than 7.5 years. Survival was the main focus of the analysis.
Using statistical formulas, the researchers estimated how many women would die from breast cancer 20 years after being diagnosed with DCIS. They calculated that 3.3% of the women would die from breast cancer. Looking at it another way, 96.7% of the women would be alive 20 years after being diagnosed with DCIS.
The risk of death from breast cancer among ALL the women diagnosed with DCIS was 1.8 times higher -- nearly double -- than that of the average woman. According to the American Cancer Society, the average woman has about a 3% risk of dying from breast cancer. So a woman who’s been diagnosed with DCIS has about a 5.4% risk of dying from breast cancer.
The researchers found that a woman’s age at DCIS diagnosis and her ethnicity were risk factors for dying from breast cancer 20 years after being diagnosed with DCIS:
- women who were diagnosed younger than age 35 had a 7.8% risk of dying from breast cancer compared to a 3.2% risk for women who were older than 35
- black women had a 7% risk of dying from breast cancer compared to a 3% risk for white, non-Hispanic women
Other factors that increased a woman’s risk of dying from breast cancer 20 years after a DCIS diagnosis were:
- larger size DCIS
- higher grade DCIS
- estrogen-receptor-negative DCIS
- being diagnosed with a second primary invasive cancer in the same breast
Radiation therapy after lumpectomy substantially reduced the risk that invasive breast cancer would come back in the same breast. Still, it didn’t result in better survival.
At first glance, because women diagnosed with DCIS had about the same risk of dying from breast cancer as women who hadn’t been diagnosed with DCIS, it might seem that DCIS should be closely monitored instead of treated.
But there are several important points to keep in mind:
- Being diagnosed with DCIS is a risk factor for invasive disease. This study didn’t look at whether the women diagnosed with DCIS had other risk factors, such as a strong family history of breast cancer or a known abnormal gene. To accurately assess a woman’s risk of invasive disease and develop a treatment plan for DCIS, doctors have to look at ALL risk factors, not just one.
- To make a DCIS diagnosis, a small piece of tissue is removed during a biopsy. While this small piece of tissue may show DCIS, it’s possible that another part of the area of concern shows evidence of invasion into the surrounding tissue. The whole area of concern has to be removed in order to be sure that the problem area is fully evaluated and treated. Your doctor can’t assume that there’s no invasion based only on the mammogram.
- Radiation often is recommended after lumpectomy for DCIS, mostly to reduce the risk of invasive disease. Radiation also lowers the risk of DCIS coming back.
- Women with diffuse DCIS were not included in this analysis; neither were women with DCIS that had microinvasion (very early signs of invasive disease).
- The standard of care for DCIS has improved a lot in the last 20 years. We have better imaging, such as digital mammograms and 3-D mammograms. There are new genomic tests, including the Oncotype DX DCIS test, which analyzes 12 genes in a DCIS and assigns a Recurrence Score, which estimates the risk of both DCIS coming back and invasive disease in the future. It gives women and their doctors more information so they can make more informed decisions about whether treatment is needed after DCIS has been surgically removed.
- This study only looked at survival as an endpoint. We don’t know how many women had to have a second surgery, perhaps mastectomy, after lumpectomy.
- Finally, this study wasn’t a randomized study, which is the most rigorous type of study. To really figure out whether careful monitoring or treating DCIS is the best option, a randomized study would have to be done:
- one group of women diagnosed with DCIS would be assigned to get surgery and possibly radiation or hormonal therapy after surgery
- the other group would be assigned to careful monitoring
Then the researchers would compare outcomes between the groups, including how many women were later diagnosed with invasive disease, as well as survival rates.
If you’ve been diagnosed with DCIS, the goal is to provide you with the best treatment for your unique situation. This takes into account:
- your family history of breast cancer and other diseases
- your personal health history
- any other breast cancer risk factors you may have
- your preferences
- the characteristics of the DCIS
- genomic test results
Together, you and your doctor will develop a treatment plan the makes the most sense for you.
For more information, visit the Breastcancer.org DCIS pages.