A radiologist compares a 2-D and 3-D mammogram in 2012. Even as nearly 60,000 women undergo surgical treatment for stage 0 cancers, the number of invasive breast cancers has not decreased. (Torin Halsey/AP)

Aggressive interventions to treat the earliest stage of breast cancers have no effect on whether a woman is alive a decade later, according to a study that tracked more than 100,000 women.

The findings, published Thursday in the journal JAMA Oncology, found that the overall risk of dying after being diagnosed with early cancer lesions, called ductal carcinoma in situ (DCIS), was 3.3 percent over two decades, and that pursuing treatment beyond a lumpectomy did not affect survival. The findings add to concerns that the ability to detect these lesions through mammograms may be leading to unnecessary mastectomies.

Women with these noninvasive cancers — a type often referred to as Stage 0 — face a frightening array of options. Most women undergo a lumpectomy to remove the abnormal cells. But the study found that adding radiation to a lumpectomy did not increase survival rates, even though it diminished the likelihood that the cancer would recur. Significantly, there was no difference in the survival rates between women with comparable tumors who had a mastectomy and those who had a less-invasive lumpectomy.

“Many women have a visceral and immediate response: ‘Get rid of my breasts,’ ” said Steven Narod, a senior scientist at the Women’s College Research Institute in Toronto who led the study. “That’s really what’s happening in the last 20 years in the U.S. We have created a culture of breast cancer awareness, and we’ve created a countercultural response of fear. When you do a mastectomy, you reduce the fear greatly.”

Outside oncologists said the study was interesting, but they were quick to point out its limitations — foremost that it wasn’t a head-to-head comparison of treatments, but rather a look back at national cancer registry data collected over two decades. That means it wasn’t possible to look at the particulars of each patient’s treatment, and several physicians said they would not change clinical practice based solely on the findings.

When Mary Lou Smith of Chicago was diagnosed with DCIS 30 years ago and again eight years ago, her doctors told her that the safest course would be to have her breasts removed. Smith, now in her 60s, opted instead to have the questionable tissue removed, which was an unusual choice. She said that although she has a bias against aggressive treatment, she understands why some doctors would recommend it and why some women would choose it despite the risks.

“There’s a lot of uncertainty in cancer and I think we don’t give it its due. It takes its toll on us. So the more certainty we can have as patients, the more comfortable we’re going to be,” she said.

The study did identify a subset of women with DCIS who were at a higher risk. Those diagnosed when they are younger than 35 and black women have a greater chance of dying from breast cancer, and more aggressive treatment may be considered, Narod said.

More broadly, the study highlights a recurring theme in cancer research: Screening has allowed doctors to detect tumors earlier but hasn’t always enabled them to distinguish between the ones that will be fatal and the ones that are slow-growing and may not affect someone’s health. That has generated a polarizing debate about whether cancers are being overtreated and how to pull back.

“I think in some of these patients, we’re overtreating them, but some others need this multidisciplinary treatment. And I think as of today . . . we cannot fully predict when a patient has cancer that is more risky,” said Mariana Chavez MacGregor, an assistant professor of breast medical oncology at the University of Texas MD Anderson Cancer Center.

Studies have found that even as nearly 60,000 women undergo surgical treatment for these Stage 0 cancers each year that are thought to be a precursor to the full-blown disease, the number of invasive breast cancers — the ones that kill — has not decreased.

A study published in June in the journal JAMA Surgery examined a similar dataset and found that in the mildest cases of DCIS, even a lumpectomy may not be necessary. That study found that surgically removing lesions from women with a subset of DCIS — low-grade lesions — did not increase survival compared with patients who did not have surgery. The study did find that surgery made a difference in survival for women with other forms of DCIS.

“It was a pretty provocative study for a surgeon to say there’s a subgroup of patients we shouldn’t be operating on,” said Mehra Golshan, a surgical oncologist at Brigham and Women’s Hospital.

The biggest critique of these kinds of studies has been that they are retrospective, looking back at what happened to women who may have chosen different treatment for different reasons. Golshan said two studies in Europe are examining what happens when women with the same diagnosis are randomly assigned to different interventions — for example, if the patients are simply observed vs. given treatment.

Ultimately, the problem may be in persuading women to accept less care.

“There are going to be a lot of women who are simply not very comfortable with that approach,” said Eric Winer, director of the breast oncology program at the Dana-Farber Cancer Institute.