Not all DCIS is dangerous, and the prognostic genomic Oncotype DX DCIS Score allows for routine risk stratification of patients to avoid unnecessary treatment.
Not all ductal carcinoma in situ (DCIS) is dangerous, and the prognostic genomic Oncotype DX DCIS Score allows for routine risk stratification of patients to avoid unnecessary treatment, reported Patrick I. Borgen, MD, chair of the department of surgery at Maimonides Medical Center in Brooklyn, New York. Dr. Borgen spoke at the 33rd Annual Miami Breast Cancer Conference, held March 10–13 in Miami Beach, Florida.
Recent jumps in DCIS diagnoses have been driven by overdetection. “There’s a reservoir of DCIS in the female breast that was never going to become invasive-or would do so, so slowly that it was never going to threaten our patient,” Dr. Borgen noted.
Graphing the utilization of mammography over time, one sees that it “completely parallels the increase in DCIS diagnoses,” Dr. Borgen said. “There’s a similar slope of percent-change over time for DCIS and mammography screening. That either means the mammograms are causing DCIS, or, much more likely, that some of this [DCIS] was not going to become clinically relevant.”
When more sensitive digital mammography became more widely used, DCIS rates jumped again, he added. “Better imaging, more DCIS.”
The prevalence of occult DCIS in autopsy studies is “about an order of magnitude higher” than what we see in screening studies, Dr. Borgen noted, as further evidence for subclinical DCIS.
Thanks to landmark prospective randomized studies like the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-17 study, the standard of care for DCIS is lumpectomy and radiation. Those studies did not identify subsets of patients who failed to benefit from radiation, but they did find that 80% of patients would do well with surgery alone. “We focus on the 10% who do better with radiotherapy, but 10% recur despite radiotherapy. The challenge is, how do we find the 80% of patients who, much later-15, 20, 25 years later-are going to be well?”
Nomograms “leave significant room for improvement,” he noted. “It is possible that clinical parameters alone are insufficient to predict outcome. We have moved away from morphology-from looking down a microscope to determine whether it’s a bad lesion.”
Instead, the field has turned to prognostic analyses of DCIS genomics.
“The Oncotype DX DCIS Score isn’t a mathematical model and doesn’t require bootstrapping,” he said. “It looks at DCIS genomics in the patient in front of you-a subset of the 21-gene assay that we use routinely.”
It has been validated in the Eastern Cooperative Oncology Group (ECOG) E5194 and Ontario DCIS Cohort studies for recurrence prognostication and risk stratification of women with DCIS who underwent breast-conserving surgery and had negative margins.
“I would argue that it’s ready for prime time” in routine clinical use, Dr. Borgen told attendees.
The DCIS Score divides patients into low, intermediate, and high-risk DCIS categories, with 65% of patients falling into the low-risk group, meaning that at 10 years, they face a 4% chance of developing invasive breast cancer.
Dr. Borgen noted that the addition of radiation doesn’t diminish the DCIS Score’s predictability. “The DCIS Score is associated with the risk of local recurrence in a population of patients with pure DCIS treated with breast-conserving surgery, with or without radiation. It’s almost certain there’s a very high-risk cohort of the disease, as well, and those patients may benefit from an entirely different treatment.”