U.K. study finds far fewer breast cancers within 3 years after DCIS detection in screening

A large British study has found a significant negative association between ductal carcinoma in situ (DCIS) cases detected at screening and invasive cancers forming in the three-year period afterward.

The connection of more DCIS findings at screening with fewer cancers later may suggest that detection and treatment of DCIS works to ward off future invasive cancers.

Either way, it comes amid the long-running debate over possible overdiagnosis and overtreatment of DCIS.

Led by Prof. Stephen Duffy, MSc, of Queen Mary University of London, a team of 18 researchers analyzed screening and 36-month interval data on 5.2 million U.K. women between 50 and 64 years old.

They found the average frequency of DCIS detected at screening to be 1.60 per 1,000 women screened, while there was a significant negative association of screening-detected DCIS cases with the rate of invasive interval cancers (Poisson regression coefficient −0.084).

At 90 percent of screening centers in the study, dispersed throughout England, Wales and Northern Ireland, the DCIS detection frequency fell within the range of 1.00 to 2.22 per 1,000 women.

Among these, for every three screen-detected cases of DCIS, there was one fewer invasive interval cancer over the next three years.

This association remained after Duffy et al. adjusted for the detection of small invasive cancers and for the detection of grade-3 invasive cancers.

While the study concentrated on statistics and didn’t track outcomes of individual patients, Duffy told the Wall Street Journal that his team’s findings “suggest that a substantial proportion of DCIS will become invasive if untreated, and it is therefore worth detecting and treating early.”

The WSJ also spoke with Otis Brawley, CMO of the American Cancer Society.

“This study tells us that diagnosing a lot of DCIS seems to lead to the prevention of some cancers,” Brawley said. “That does not mean that all DCIS needs to be diagnosed or treated.”

And the beat goes on.