Fewer mammograms mean more positive nodes?

Fewer mammograms mean more positive nodes?

5/12/2013

CHICAGO -- The frequency of mammography may not have an impact on the size of tumors when they're discovered, but fewer screens may be associated with more lymph node positivity, researchers reported here.

In a single-center retrospective study, there were no significant differences in tumor size or in stage 0 or 1 disease whether women had scans every year or every 3 years, according to Lilian Wang, MD, of Feinberg School of Medicine at Northwestern University, and colleagues.

But those who were screened every 1.5 to 3 years, or at longer intervals than 3 years, had significantly higher rates of lymph node positivity than those who were screened at close to an annual basis, they reported at the Radiological Society of North America meeting here.

"Women screened at intervals less than one-and-a-half years are statistically less likely to have cancer spread to their lymph nodes," Wang said during a press briefing, adding that these findings support the recommendations of several advocacy organizations.

And previous work has shown that lymph node positivity is associated with worse disease and worse outcomes, particularly in terms of mortality.

Although the U.S. Preventive Services Task Force in 2009 recommended against annual mammography beginning at age 40 -- instead suggesting biennial screens from ages 50 to 74 -- most insurers have been covering annual screening because several cancer and radiology groups harshly criticized the guideline.

The USPSTF has also somewhat backpedaled on the recommendation, and last month announced a draft research plan to guide a systematic review of the evidence on breast cancer screening to develop an updated recommendation, Wang said.

Wang said she hopes the study will be "used in the revision of those recommendations. She and colleagues conducted a retrospective study of 332 women with breast cancer identified on mammography at Northwestern Memorial Hospital from 2007 to 2010.

They divided the women into three groups based on the length of time between screenings: less than 1.5 years, 1.5 to 3 years, and more than 3 years.

Overall, they found no significant difference in the percentage of early-stage (stages 0 or 1) detected, nor in the percentage of women diagnosed with minimal cancer.

And there was no statistically significant difference in tumor size at discovery either, they found.

But they did find that women in the most frequently screened group had far lower rates of lymph node positivity: 8.7% compared with 20.5% for those in the 1.5-to-3-year interval group and 15.4% among those who were screened at greater than 3-year intervals (P=0.023).

Gary Whitman, MD, professor of radiology at MD Anderson Cancer Center in Houston, who was not involved in the study, called the data "fairly strong" that annual mammography "is quite beneficial."

"If we wait longer for screening, the likelihood of axillary disease is higher," he said. "So it's important to aim for mammography less than every one-and-a-half years."

 

Source: MedPage Today: http://www.medpagetoday.com/MeetingCoverage/RSNA/43261