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

March 15, 2025

There is growing concern about the overtreatment of DCIS.  Overtreatment is the treating of a disease or condition even though it may not have led to symptoms in a patient’s lifetime or earlier mortality.  

DCIS is sometimes referred to as a “non-obligate precursor” of breast cancer.  Non-obligate precursor means that it can, but often does not, lead to invasive breast cancer.  Some studies estimate that as much as 50-80% of DCIS, if left untreated, would remain harmless in a patient’s lifetime.  Yet even though most cases of DCIS might be able to avoid treatment, because doctors cannot reliably predict which cases those are, virtually all are treated.  This means that many women are potentially undergoing treatment for premalignant conditions that are unlikely to develop into life-threatening cancers. 

The problem is compounded by the fact that standard treatments for DCIS are aggressive: surgery (either mastectomy or lumpectomy), radiation in some cases, and for hormone-positive DCIS, five years of hormone therapy.  All of these treatments have short- and long- terms physical and emotional side effects. 

How Did We Get Here?

Prior to the rise of mammography in the mid-1980s, DCIS was uncommon, making up only 3% of breast cancer diagnoses.  Mammographic screening has led to the detection of very early cancers, including the detection of abnormal cells that look like cancers but may or may not actually be precursors of invasive disease, as is the case with DCIS.  Today, DCIS makes up approximately 25% of screen-detected breast cancer diagnoses, with nearly 60,000 cases annually in the U.S. alone.  

Initially, it was presumed that because DCIS looked similarly to invasive breast cancer, that it would behave similarly, and therefore the removal and treatment of DCIS would lead to an overall decline in incidence and deaths from breast cancer.  Curiously, the treatment of 60,000 DCIS cases annually does not appear to have decreased invasive breast cancer diagnoses; in fact, we have witnessed the opposite: invasive breast cancer is on the rise, especially among younger woman, with nearly 317,000 estimated diagnoses for 2025.  

Over time, researchers have changed their view of cancer.  We now know that not all early cancers inevitably grow and spread, and some can remain in place and never cause harm to a patient.  The challenge has been determining which cases of DCIS fall into that category.  In the meantime, every case is treated.

What Have We Learned from Studies?

In 2015, 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%).  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 significantly affect her risk.

Another study looked at breast cancer mortality rates for 57,222 patients with low-grade DCIS over 10 years, and found no difference in risk between patients who had surgery and those who did not.  The study suggests that many low-risk patients may be more likely to die of a cause other than breast cancer, regardless of whether they have surgery, and therefore surgery may not be necessary.

Clinical trials are underway in the U.S., Europe and Japan investigating whether active monitoring of low-risk DCIS, in some cases paired with hormone therapy, is a safe alternative to the more aggressive treatments of surgery and radiation.  The first results from the U.S.-based Comparing an Operation to Monitoring, with or without Endocrine Therapy (COMET) trial have suggested that it is, at least in the short-term.  

Where Do We Go from Here?

Studies like COMET a provide hope for a potential treatment de-escalation option in some low-risk DCIS cases.  However, to keep pace with the rapid increase in DCIS diagnoses, more research is needed – both clinical trials as well as laboratory research to better understand the biology of DCIS and what causes DCIS cells to turn malignant.

In the meantime, we need to fast-track information to patients and doctors on the emerging DCIS research and clinical trials.  We need to encourage doctors to provide individualized, patient-centered care for their DCIS patients, with improved patient-physician communication at its core.  We need to educate patients about what DCIS is (and what it isn’t), their likely risk of developing invasive breast cancer, and the pros and cons of varying treatment options, so they can make a balanced and informed decision about how best to proceed upon receiving a DCIS diagnosis.

More research and education are critical to ensuring that we manage DCIS in the best way possible: providing treatment for those patients who need it while avoiding the overtreatment of those who do not.

Last Updated March 15, 2025

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