Applying research to practice

Responsible use of breast cancer screening


 

In this edition of “Applying research to practice,” I examine a study suggesting that annual screening mammography does not reduce the risk of death from breast cancer in women aged 75 years and older. I also highlight a related editorial noting that we should optimize treatment as well as screening for breast cancer.

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Regular screening mammography in women aged 50-69 years prevents 21.3 breast cancer deaths among 10,000 women over a 10-year time period (Ann Intern Med. 2016 Feb 16;164[4]:244-55). However, in the published screening trials, few participants were older than 70 years of age.

More than half of women above age 74 receive annual mammograms (Health, United States, 2018. www.cdc.gov/nchs/data/hus/hus18.pdf). And more than a third of breast cancer deaths occur in women aged 70 years or older (CA Cancer J Clin. 2016 Mar-Apr;66[2]:96-114).

Do older women benefit from annual mammography to the same extent as younger women? Is there a point at which benefit ends?

To answer these questions, Xabier García-Albéniz, MD, PhD, of Harvard Medical School in Boston, and colleagues studied 1,058,013 women enrolled in Medicare during 2000-2008 (Ann Intern Med. 2020 Feb 25. doi: 10.7326/M18-1199).

The researchers examined data on patients aged 70-84 years who had a life expectancy of at least 10 years, at least one recent mammogram, and no history of breast cancer. The team emulated a prospective trial by examining deaths over an 8-year period for women aged 70 years and older who either continued or stopped screening mammography. The researchers conducted separate analyses for women aged 70-74 years and those aged 75-84 years.

Diagnoses of breast cancer were, not surprisingly, higher in the continued-screening group, but there were no major reductions in breast cancer–related deaths.

Among women aged 70-74 years, the estimated 8-year risk for breast cancer death was reduced for women who continued screening versus those who stopped it by one death per 1,000 women (hazard ratio, 0.78). Among women aged 75-84 years, the 8-year risk reduction was 0.07 deaths per 1,000 women (HR, 1.00).

The authors concluded that continuing mammographic screening past age 75 years resulted in no material difference in cancer-specific mortality over an 8-year time period, in comparison with stopping regular screening examinations.

Considering treatment as well as screening

For a variety of reasons (ethical, economic, methodologic), it is unreasonable to expect a randomized, clinical trial examining the value of mammography in older women. An informative alternative would be a well-designed, large-scale, population-based, observational study that takes into consideration potentially confounding variables of the binary strategies of continuing screening versus stopping it.

Dr. Alan P. Lyss, now retired, was a community-based medical oncologist and clinical researcher for more than 35 years, practicing in St. Louis.

Dr. Alan P. Lyss

Although the 8-year risk of breast cancer in older women is not low among screened women – 5.5% in women aged 70-74 years and 5.8% in women aged 75-84 years – and mammography remains an effective screening tool, the effect of screening on breast cancer mortality appears to decline as women age.

In the editorial that accompanies the study by Dr. García-Albéniz and colleagues, Otis Brawley, MD, of Johns Hopkins University, Baltimore, highlighted the role of inadequate, ineffective, inconvenient, or poorly tolerated treatment in older women (Ann Intern Med. 2020 Feb 25. doi: 10.7326/M20-0429).

Dr. Brawley illustrated that focusing too much on screening diverts attention from the major driver of cancer mortality in older women: suboptimal treatment. That certainly has been the case for the dramatic impact of improved lung cancer treatment on mortality, despite a statistically significant impact of screening on lung cancer mortality as well.

As with lung cancer screening, Dr. Brawley describes the goal of defining “personalized screening recommendations” in breast cancer, or screening that is targeted to the highest-risk women and those who stand a high chance of benefiting from treatment if they are diagnosed with breast cancer.

As our population ages and health care expenditures continue to rise, there can be little disagreement that responsible use of cancer diagnostics will be as vital as judicious application of treatment.

Dr. Lyss was a community-based medical oncologist and clinical researcher for more than 35 years before his recent retirement. His clinical and research interests were focused on breast and lung cancers as well as expanding clinical trial access to medically underserved populations.

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