Breast Screening for Women over 70 Does Not Result in Sharp Drop in Advanced Disease

Breast screening for women over age 70 does not prompt a sharp fall in advanced disease. Instead, it may just lead to overdiagnosis and overtreatment, suggests new findings by Dutch researchers.

The researchers led by a team based at Leiden University Medical Center (The Netherlands) are presenting their data at the Preventing Overdiagnosis Conference, held September 15–17, 2014, in Oxford (UK), where experts worldwide will discuss how to handle the threat to health and the waste of money caused by unnecessary care. The conference is hosted by the Center for Evidence-Based Medicine at the University of Oxford (UK) in partnership with the British Medical Journal (BMJ) "Too Much Medicine campaign."

The upper age limit for the national breast cancer screening program was extended to women aged 69 to 75 in 1998 in the Netherlands, and national guidelines now recommend screening women up to the age of 75. This is in spite of no strong evidence showing that screening much older women is effective, according to the researchers, due to the scarcity of this age group in any of the clinical trials on which the policy is founded. However, breast cancer is the most common cancer and biggest cause of death from cancer in women worldwide. Furthermore, as populations age, the percentage of older women who are diagnosed with the disease is set to increase in the developed world.

The researchers therefore set out to find whether the national breast screening program in the Netherlands has made a significant impact in the numbers of late stage cancers among 70–75 year old—a hallmark of success. They monitored all new cases of invasive and non-invasive (in situ) breast cancer, diagnosed in this age group from 1995 up to 2011, using data from the Netherlands Cancer Registry. They separated cases into the period before (1995-7), after (2003-11), and in-between (1998-2002) the introduction of the national screening program, which came to almost 25,500 in all. Furthermore, they included 13,000 women aged 76–80, to take account of any changes in breast cancer incidence among older women ineligible for national screening.

Data analysis showed that new cases of early stage breast cancer among 70–75 year olds rose sharply after national screening was introduced, from 248.7 to 362.9 per 100,000 women. However, while there was a substantial decrease in the numbers of new cases of advanced breast cancer, the absolute decrease was small; dropping from 58.6 before, to 51.8 instances per 100,000 women after, the national screening program was introduced.

Among 76–80 year olds, new cases of early stage disease fell slightly, but the numbers of new cases of advance breast cancer did not change. The researchers calculated, based on the figures, that for every advanced stage cancer detected by screening among 70–75 year olds, around 20 “extra” and therefore “overdiagnosed” early stage tumors are identified, which the researchers described as a “considerable proportion.”

Overdiagnosis and overtreatment are important, the researchers emphasized, because they can undermine quality of life, and because older individuals are more susceptible to the side effects of breast cancer treatment. Moreover, they come with a potentially huge cost in return for little obvious health benefit, the investigators pointed out. “Instead of using mass screening, the decision to participate in the screening program should be personalized, based on remaining life expectancy, breast cancer risk, functional status and patients’ preferences,” the authors concluded.

The study’s findings were published September 16, 2014, in the British Medical Journal (BMJ).

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Leiden University Medical Center