AMSTERDAM—Women diagnosed with ductal carcinoma in situ (DCIS) of the breast were found to live longer than women in the general population, according to a study from the Netherlands reported at the 2017 European Cancer Congress (ECCO).
“It may sound a bit counterintuitive—but we found that DCIS patients older than 50 at diagnosis were at lower risk of dying compared to the general population,” said Lotte Elshof, MD, PhD, Student Associate of the Departments of Surgery, Epidemiology, and Molecular Pathology at the Netherlands Cancer Institute in Amsterdam.
“We think it is because these patients are mostly screen detected so they go to the population-based screening program for breast cancer and are likely to be more health conscious,” she said.
The findings she reported were associated with the ongoing randomized, non-inferiority phase III “LORD” trial being conducted in the Netherlands by the BOOG (Borstkanker Onderzoek Groep) team under principal investigator Jelle Wesseling, MD, PhD, Consultant Breast Pathologist at the Netherlands Cancer Institute in Amsterdam, looking at “management of low grade ductal carcinoma in situ: active surveillance or not?”.
Elshof explained that they looked at patients being treated for DCIS because it was a potential precursor lesion to invasive breast cancer.
“If [patients] had died, we assessed cause-specific mortality [to] see from what cause they had died. And then we compared [their] mortality with mortality in the general population,” she said.
The study found that patients with DCIS had lower risk of dying of all causes combined compared to the general population and “seem to represent a generally healthy subgroup.”
Also, their absolute risk of breast cancer death was low—3.9 percent at 15 years—and the risk of dying from breast cancer among women treated for DCIS alone was only slightly higher than that in the general population.
The suggestion was that “a history of primary DCIS has no negative effect on overall survival.”
The study looked at 9,799 women treated for DCIS in the Netherlands from 1989 to 2004. Over a median follow-up of 10 years, 1,429 deaths occurred of which 368 were due to cardiovascular disease (4% of the total population) and 284 deaths were due to breast cancer (3%).
These data revealed an overall risk of dying of all causes that was significantly lower combined compared to the general population.
“There are a lot of uncertainties and anxiety associated with DCIS because many patients think they are diagnosed with breast cancer. Some DCIS lesions will progress into invasive breast cancer and can metastasize and then cause death. So it's important to look at the outcomes,” Elshof said.
Breast Cancer-Specific Risk
Although the study confirmed patients with DCIS were at increased risk of dying from breast cancer they still had a lower risk of dying overall despite this.
“If we look at absolute numbers, the risk is very low,” she said. “After 10 years 2.5 percent of the women died from breast cancer—but compared to the general population this is only a slightly increased risk.”
Intriguingly, the study also found that the risk of dying from breast cancer was independent of the type of treatment patients received.
“We found that no matter what treatment, the risk of mortality was low. We compared women treated with breast conserving therapy alone, breast conserving therapy with radiotherapy, and mastectomy. And we saw no differences in breast cancer mortality,” she explained.
When she was asked what was the practical message for cancer clinicians, she said the study provided accurate estimates of relative and absolute risk, which she regarded as important information for the patient.
“These patients should be told they have a precursor lesion of invasive breast cancer but not yet invasive breast cancer. And it should provide reassurance,” she said.
“[DCIS is] a very worrying diagnosis. It's associated with a lot of anxiety and confusion. It means that we sometimes find lesions that we would have rather not detected. But because of screening, we find those lesions and the screening program also has a lot of benefits. So it's not that we say we don't need to screen, but there are always harms against benefits. And some DCIS detection would be beneficial,” said Elshof.
She concluded that doctors could now accurately explain the diagnosis of DCIS, tell patients what it is, and reassure them they have the same life expectancy as other women.
Philip Poortmans, MD, PhD, President-Elect of ECCO and Head of the Radiation Oncology Department at Radboud University Medical Center in Nijmegen, in The Netherlands, said that, although ductal carcinoma in situ should be considered as being clearly different from breast cancer, treatments had side effects.
“This research provides reassurance for women with DCIS because it shows that they are as likely to be alive 10 years after the diagnosis as people in the general population who did not have DCIS. This is also reassuring with regards to the potential risks of side effects,” he said.
“However, we have to recognize that in one-fifth of patients who die, the cause is breast cancer—which is likely to result from progression of the DCIS they were diagnosed with. Therefore, we are eagerly waiting results of further research to identify factors—including age, as clearly shown in this study—that contribute to the risk for recurrence and progression from DCIS for each individual patient.”
Poortmans thought it was remarkable that the increased risk of dying from breast cancer was completely offset by a lower risk of dying from other causes compared to women in the general population.
“This might be explained by the generally better health and socioeconomic status of women who regularly participate in breast cancer screening. This could also be tested in the ongoing research,” he concluded.
Peter M. Goodwin is a contributing writer.