DCIS May Be Overtreated
A study of more than 100,000 women who were diagnosed with stage 0 breast cancer – known as DCIS – shows preventing higher-stage disease from developing did not prevent a statistically significant number of breast cancer deaths. The research was published in JAMA Oncology.
About 20 percent of breast cancers that are found using a mammogram are ductal carcinoma in situ, or DCIS, also called stage 0 breast cancer. DCIS is found in the breast ducts, tubes that carry milk to the nipple. It is non-invasive cancer, because it has not yet spread to other parts of the breast or beyond. All stages above 0 are considered invasive.
Very few women diagnosed with DCIS die of breast cancer. Of those women, some, though not all, are eventually diagnosed with an invasive breast cancer as well. These researchers wanted to find out how many women died of breast cancer after a DCIS diagnosis, how different treatments affected the risk of dying and if any risk factors were associated with death from breast cancer after DCIS.
Using the Surveillance, Epidemiology, and End Results (SEER) 18 registries research database, researchers looked at women who were diagnosed with DCIS before age 70, between 1998 and 2011.
They found 108,196 eligible women, for whom the following information was available:
- Year of and age at diagnosis
- Race and ethnicity
- Income level
- Features of the cancer
- Course of treatment
- Date of a second primary breast cancer (if it occurred)
- Cause of death
- Length of survival
The average amount of follow-up time was 7.5 years. The researchers looked at how many of these women had died, or based on statistics, were predicted to have died, of breast cancer within 10 and 20 years after a DCIS diagnosis. They also looked at how their risk of dying from breast cancer compared to that of women in the general population, who had not been diagnosed with DCIS.
The most notable finding of this study is that while different treatments were associated with different risks of invasive recurrence in the same breast, they made little difference in survival. The percentage of women who died of breast cancer was:
- .4 percent of women who had a lumpectomy and radiation
- .5 percent of women who had a lumpectomy without radiation
- .6 percent of women who had a mastectomy
Ten years after a DCIS diagnosis, about 1.1 percent of the women were predicted to have died of breast cancer. Twenty years after a DCIS diagnosis, about 3.3 percent of the women were predicted to have died of breast cancer.
More than half the women in the study who died from breast cancer didn’t experience a documented invasive recurrence in either breast.
Age and Ethnicity
Women diagnosed with DCIS were 1.8 times more likely to die of breast cancer than women in the general population. This risk went down for women older than 65 at diagnosis, who were 1.4 times more likely to die of breast cancer than women in the general population.
Very few women in the study – just 1.2 percent – were diagnosed with DCIS before age 35, but their risk of dying of breast cancer was about 17 times higher than women in the general population. Among the study participants with DCIS, black women were about 2.55 times more likely to die than non-Hispanic white women.
Women with DCIS that didn’t grow in the presence of the hormones estrogen or progesterone were more likely to die during the first 10 years than women with DCIS that did grow because of those hormones. But during the second 10 years, the opposite was true.
Tumor grade, how abnormal the cancer cells look under a microscope and how quickly the tumor is likely to grow and spread, did not make a difference in a woman’s risk of developing an invasive recurrence in the same breast. But women with high-grade DCIS were about 1.88 times more likely to die of breast cancer than women with low-grade DCIS.
A randomized clinical trial, in which people are assigned to different treatments, would strengthen these findings. This study was observational, looking at information after the fact, so its results are not as strong.
What This Means for You
Many studies of DCIS use prevention of a local recurrence as a sign that treatment worked. But this study suggests that preventing local recurrence doesn’t mean preventing death from breast cancer. Considering that, the study’s authors suggest that local therapies like mastectomy and radiation, and maybe even lumpectomy, aren’t necessary for women with DCIS, because they don’t appear to save lives.
Having fewer and less extensive treatments can be less costly, for your body and your wallet, and it may help you preserve a healthy body image. But doing more may help lower your fear of recurrence, because it may comfort you to feel you took action.
It’s important to keep in mind that breast cancer doctors know that women with DCIS have a low risk of dying of breast cancer, but they don’t necessarily believe these findings mean women with DCIS should immediately start receiving less treatment. More research is needed, and this study is likely to inspire researchers to look at this issue more closely. But because so few people die of breast cancer after DCIS, creating a randomized clinical trial to look at this issue will be difficult.
If you’ve recently been diagnosed with DCIS and haven’t yet made treatment decisions, talk to your healthcare providers about what they think of this study and why or why not, and how, they think it should affect your treatment plan.
If you were treated for DCIS in the past, this study may cause you to question whether you received the right kind of treatment. Know that you and your doctors made the decisions that you felt were best for you at the time, decisions that many doctors will continue to recommend despite this research. Regardless of what treatments you had, your risk of dying from breast cancer after DCIS is very low.
Irwin, ML, Cartmel, B, Gross, CP, et al. Breast Cancer Mortality After a Diagnosis of Ductal Carcinoma In Situ. The Journal of the American Medical Association. Published online August 20, 2015. doi:10.1001/jamaoncol.2015.2510.