Do Fewer Mammograms Translate to More Positive Nodes?

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Based on a new study, the occurrence of mammography may not have an affect on the size of tumors when they're detected, but fewer screens may be linked to more lymph node positivity.

According to Lilian Wang, MD, of Feinberg School of Medicine at Northwestern University, and peers, there were no major differences in tumor size or in stage 0 or 1 disease whether women had scans every year or every 3 years.

However, those who were screened every 1.5 to 3 years, or at longer periods than 3 years, had considerably higher rates of lymph node positivity as opposed to those who were screened at close to an annual regimen. The team presented their findings at the Radiological Society of North America annual meeting.

“Women screened at intervals less than one-and-a-half years are statistically less likely to have cancer spread to their lymph nodes," said Wang, 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.”

And although the U.S. Preventive Services Task Force (USPSTF) in 2009 recommended against annual mammography starting at the age of 40, instead opting for biennial screens from ages 50 to 74, most insurers have been covering annual screening because several cancer and radiology groups scathingly criticized the guideline.breast-imaging

“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,” said Wang.

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 separated the women into three different 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 major difference in the percentage of early-stage (stages 0 or 1) detected, nor in the percentage of women diagnosed with minimal cancer.

Additionally, there was no statistically important difference in tumor size at discovery either.

However, they did discover that women in the most regularly screened group had far lower rates of lymph node positivity: 8.7% as opposed to 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).

Professor of radiology at MD Anderson Cancer Center in Houston, Gary Whitman, MD, 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. So it's important to aim for mammography less than every one-and-a-half years,” he said.

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