Why is DCIS Often Overtreated and What Can We Do About It?

How Did We Get Here?

Prior to the rise of mammography in the mid-1980s, DCIS was relatively uncommon, accounting for only about 3% of breast cancer diagnoses. The rise of screening mammography led to increased detection of very early-stage abnormalities, including DCIS – cells that appear cancerous but may or may not progress to invasive disease.

Today, DCIS accounts for approximately 20–25% of screen-detected breast cancer diagnoses, with nearly 60,000 cases diagnosed each year in the United States.

Initially, because DCIS resembles invasive breast cancer under the microscope, it was assumed that it would behave similarly. The expectation was that detecting and treating DCIS would reduce the incidence of invasive breast cancer and breast cancer mortality.

However, despite decades of treating DCIS, this expected reduction has not occurred. Invasive breast cancer rates have not declined in proportion to increased DCIS detection, and in some populations, rates are rising – particularly among younger women.

Over time, the scientific understanding of cancer has evolved. We now know that not all early-stage or abnormal cells will progress to life-threatening disease. Some may remain indolent and never cause harm. The challenge has been identifying which cases of DCIS fall into that category. In the absence of that ability, most cases continue to be treated. 

What Have We Learned from Studies?

Research on DCIS continues to evolve, and much of the current evidence comes from observational studies and ongoing clinical trials.

A large observational study of over 100,000 women with DCIS followed for 20 years found no significant difference in breast cancer mortality between those treated with mastectomy and those treated with lumpectomy (with or without radiation). In both groups, the risk of dying from breast cancer was low – about 3.3% – only slightly higher than that of the general population (about 2.5%). This suggests that not only does more aggressive surgery not seem to affect a DCIS patient’s long-term risk of dying from breast cancer, but any surgery at all may not affect her risk.

Another study examining more than 57,000 patients with low-grade DCIS over 10 years found no difference in breast cancer mortality between those who underwent surgery and those who did not. These findings suggest that some patients with low-risk DCIS may be more likely to die of other causes than from breast cancer, regardless of treatment.

More recent observational data add to this picture. A 2025 BMJ study following 1,780 women with DCIS who did not undergo upfront surgery found low breast cancer mortality and relatively modest rates of progression to invasive cancer, with about 8–14% developing invasive cancer over eight years, depending on risk. These shorter-term findings differ from older lifetime modeling estimates (often cited at 20–50%), which attempt to project long-term outcomes using different assumptions and methods. While the study has important limitations – including its observational design, potential selection bias, and relatively short follow-up – it provides additional evidence that some cases of DCIS may be safely managed without immediate treatment.

It is important to note that these studies have limitations and do not fully capture the natural history of untreated DCIS, underscoring the need for more research.

Prospective clinical trials are now underway in the United States, Europe, and Japan to better answer these questions. These trials are evaluating whether active monitoring (active surveillance) – sometimes combined with endocrine therapy – may be a safe alternative to surgery and radiation for carefully selected patients with low-risk DCIS.

Early results from the U.S.-based COMET trial suggest that, at least in the short term, active monitoring may be a safe option for some patients.

Where Do We Go from Here?

Studies like COMET offer promising evidence that future treatment de-escalation may be appropriate for some patients. However, more research is needed to better understand the biology of DCIS and to develop reliable tools for predicting which cases are likely to progress.

At the same time, there is a need to more rapidly translate emerging research into clinical practice. This includes improving communication between patients and providers and supporting more individualized, patient-centered decision-making.

Patients should be informed about:

• What DCIS is – and what it is not
• Their estimated risk of developing invasive breast cancer, as best as can be determined based on pathology and other risk factors
• The potential benefits and risks of different treatment approaches

This information can help patients make more informed and balanced decisions about their care.

The Bottom Line

There is increasing evidence that DCIS is overtreated, largely because current tools cannot reliably distinguish between lower and higher risk. At the same time, DCIS is not risk-free, and treatment remains important for some patients.

Advancing research, improving risk stratification, and supporting informed, shared decision-making are essential to ensuring that patients receive care that is both appropriate and personalized.

Last Updated March 19, 2026