Understanding Risk & Making Decisions

DCIS is not well understood and treatments are aggressive, so it is important to work with your doctor to assess your risk before making any decisions. Risk refers to the chance, odds, or probability that something will or will not happen. In the context of DCIS, risk refers to the probability of future invasive breast cancer or additional DCIS.

Ideally, you would determine your individual risk, which is the chance that YOU, as an individual, could get invasive breast cancer. Unfortunately, this is difficult to measure with specificity because there are so many factors to consider, many of which, such as diet and lifestyle, are not quantifiable.

That said, it can be helpful to think about where you stand on a spectrum of risk, ranging from very low to very high. To do that, you can look at your individual risk profile, which includes your pathology report (designating the size, grade and hormone-receptor status of your DCIS), genetic or other testing results, family history, age, environment, stress level, and lifestyle habits such as diet and exercise. Your individual risk profile does not provide a specific probability, but rather looks at a number of risk-influencing factors that, when viewed together, can help you and your doctor make an educated guess as to where you stand on a spectrum of risk.

You can also look at data from research studies of DCIS patients that assess absolute risk. Absolute risk is the actual probability of DCIS progressing to invasive breast cancer in a specific group of people. Understanding absolute risk is important because it can help you make informed treatment decisions based on your individual risk profile.

Studies Assessing Risk in DCIS Patients

DCIS did not become a common diagnosis until the advent of mammography in the mid-1980s, and for decades the assumption was that all DCIS should be treated the same (with surgery and radiation). Over time, researchers learned that there are different types of DCIS and studies suggested that there may be other treatment strategies, especially for low-risk DCIS. More research is needed to better understand risk in DCIS patients, but we have learned the following:

As all DCIS is currently treated, we have limited data as to its natural progression. That said, studies estimate that as much as 50-80% of DCIS will not progress to invasive breast cancer in a woman’s lifetime, and 20-50% will progress.¹,²,³
Surgery will reduce your risk of DCIS recurrence or future invasive breast cancer. Women treated with a lumpectomy have a slightly higher risk of recurrence than women who undergo a mastectomy.
There are side effects from surgery. Side effects vary from patient to patient. Risks of side effects and complications are higher for mastectomy than lumpectomy.
There are side effects from radiation and hormone therapy. Side effects vary from patient to patient.
Choosing between a lumpectomy, mastectomy, and for low-risk DCIS, any surgery at all, is not likely to impact your breast cancer mortality rate, which is your long-term risk of dying of breast cancer. An observational study of 108,196 DCIS patients over 20 years found there was no difference in breast cancer mortality rates between women treated with mastectomy and those treated with lumpectomy (with or without radiation). In both groups, the risk of dying of breast cancer was very low, only 3.3 percent, which is very close to the odds that an average woman will die of breast cancer (about 2.5%). Another study demonstrated that there was no difference in breast cancer mortality rates after 10 years between low-grade DCIS patients who had surgery and those who did not have surgery.
There are clinical trials underway in the U.S., Europe and Japan investigating the safety and feasibility of active monitoring for the management of low-risk DCIS.
In the U.S., the Comparing an Operation to Monitoring, with or without Endocrine Therapy (COMET) trial, is a phase III randomized clinical trial comparing rates of invasive breast cancer and physical, emotional and psychological outcomes for women following active monitoring as compared to women who received standard of care treatments. The first results of COMET were released in December 2024 and showed comparable outcomes for women in both treatment arms, suggesting that active monitoring is a safe and reasonable treatment approach for low-risk patients, at least in the short term.

Other Considerations and Thinking About Trade-offs

In addition to assessing your individual risk profile, there are other factors you may consider in making treatment decisions. These include your family, quality of life, personal preferences, emotional/psychological impacts, work obligations and financial considerations.

A helpful decision-making strategy is assessing your trade-offs, that is, what you are willing to give up in order to gain something else. Trade-offs are not quantifiable and highly individualized based on a patient’s unique circumstances and preferences. Examples of trade-offs include:

Choosing more aggressive surgery (mastectomy) to avoid adjuvant treatments (radiation and/or hormone therapy) and their side effects.
Choosing less aggressive surgery (lumpectomy) to avoid the side effects of more aggressive surgery (mastectomy, with possible reconstruction).
Choosing to avoid radiation for DCIS so to preserve that treatment option for possible future invasive breast cancer.
For low-risk DCIS, choosing active monitoring, with or without hormone therapy, to avoid the side effects from more aggressive treatment (surgery, with or without radiation).
Choosing a more or less aggressive approach because of how you anticipate it will impact other factors that are important to you, such as your psychological state or family obligations.

There are risks and trade-offs with all DCIS treatment strategies. It is important to understand what these risks and trade-offs are, and take the time to explore your options, so that you can feel comfortable in your decision.

Rosenberg, Shoshana M. et al., “Is it Cancer or Not?” A Qualitative Exploration of Survivor Concerns Surrounding the Diagnosis and Treatment of Ductal Carcinoma in Situ (DCIS). Cancer. Published April 15, 2022. [PubMed: 35191017] ↩︎
Byng, Danalyn, et. al., Treating (Low-Risk) DCIS Patients: What Can We Learn from Real-World Cancer Registry Evidence? Breast Cancer Res. Treat. Published online January 3, 2021. [PubMed: 33389397] ↩︎
Erbas, Bircan, et al., The Natural History of Ductal Carcinoma in Situ of the Breast: A Review. Breast Cancer Res. Treat. May 2006. [PubMed: 16319971] ↩︎