A recent article published Thursday in JAMA Oncology, the most extensive collection of data on ductal carcinoma in situ (DCIS) collected and published to date, suggests that surgery for DCIS may not make a difference in outcomes for most women.

DCIS is a noninvasive type of breast cancer. The cancer is considered noninvasive because it remains confined to the milk ducts. Also called Stage 0 cancer, the abnormal cells may never break free and invade the surrounding breast tissue. Some may go away on their own without treatment. Other cases of DCIS might remain for a woman’s entire lifetime without causing her problems or requiring treatment. But some doctors also have concerns that some cases of DCIS will turn invasive and spread throughout the body. Treatment for DCIS typically involves some kind of surgery (lumpectomy or mastectomy) and may also involve other treatments such as radiation therapy or hormonal therapies. Until now, we have not had enough data to answer these questions or to tell doctors whether our current forms of treatment for DCIS are actually making a difference for patients.

In the study, 100,000 women with DCIS were followed for 20 years. Nearly all of the women in the study had some form of surgery (either lumpectomy or mastectomy) and their chance of dying from breast cancer was found to be 3.3% regardless of which surgery they had performed – this is the same risk as an average woman’s risk of dying with breast cancer.

The data also suggests that treating DCIS does not seem to prevent the development of invasive breast cancers: there was no difference in the rate of invasive breast cancers seen in the women who had surgery in the study. An editorial that accompanied the paper discussed that if treating DCIS was preventing invasive cancers than we should have seen a reduction in the incidence of invasive breast cancers as we have found and treated more cases of DCIS, which has not happened. The study did show that some women are at a higher risk of death with DCIS than others: women who are younger than age 40, African American women, and women with aggressive tumor markers. For these women, the death rate over the 20 year period was about 7.8%.

Some clinicians suggest that this new data raises questions as to whether or not surgery should be considered for DCIS patients while others still believe that we need more data that shows that a “watch and wait” approach for DCIS would not lead to an increased risk for invasive cancers or increased mortality. While the data in this study is compelling, so few women diagnosed with DCIS opted out of surgery it is not possible to accurately compare the cancer and mortality rates for those who did not have surgery to those who did. For now, it is unlikely that many doctors will be suggesting a “wait and watch” approach on DCIS anytime soon, but it is important for women with DCIS to know that there are no definitive answers about the treatment. Having all the information about what we know (and do not know) about the treatment of DCIS, personal risk factors, and the potential benefits and risks about the various treatment options can ensure that each woman and her physicians can make the best treatment decision possible.