Women older than age 75 years may not benefit from continued screening with mammography, according to a new study.
Researchers used Medicare data from 1999 to 2008 to perform a population-based, observational study examining two screening strategies: continuing annual mammography after a certain age or ceasing to screen. The goal of the study was to estimate the effect of breast cancer screening on death from breast cancer in Medicare beneficiaries ages 70 to 84 years. The primary outcome measures were breast cancer mortality, incidence, and treatment over eight years, as well as the positive predictive value of screening mammography by age group. The study results were published Feb. 25 by Annals of Internal Medicine.
A total of 1,058,013 women were included in the study. All had a life expectancy of at least 10 years, had not been previously diagnosed with breast cancer, and had undergone screening mammography. Overall, 1,533 breast cancer deaths occurred during follow-up with the “continue screening” strategy and 1,304 occurred under the “stop screening” strategy. The estimated difference in risk for breast cancer between continuing screening and stopping screening over eight years was −1.0 (95% CI, −2.3 to 0.1) death per 1,000 women (hazard ratio, 0.78; 95% CI, 0.63 to 0.95) among women ages 70 to 74 years, with a negative risk difference favoring continued screening. In women 75 to 84 years of age, however, this risk difference was 0.07 (95% CI, −0.93 to 1.3) death per 1,000 women (hazard ratio, 1.00; 95% CI, 0.83 to 1.19). Women whose breast cancer was diagnosed under the “stop screening” strategy were more likely to receive chemotherapy but less likely to receive radiotherapy, lumpectomy, or other surgery than those whose breast cancer was diagnosed under the “continue screening” strategy.
The authors noted that data were only available for eight years of postscreening follow-up and that their results could have been affected by residual confounding. They concluded that continuing annual mammography after age 75 years did not substantially reduce breast cancer mortality at eight years versus stopping screening. “The reduced benefit in older women is consistent with the hypothesis that competing causes of death, such as cardiovascular or neurologic conditions, overtake breast cancer mortality with increasing age,” the authors wrote.
An accompanying editorial noted that the study used data from 1999 to 2008, when digital mammography was first being introduced, and pointed out that almost all mammography is now digital and 3D mammography or tomosynthesis is also common. One-third of American women who die of breast cancer are diagnosed after age 70 years, the editorialist wrote, but evidence does not show that mammography after age 75 years is of much benefit, and the benefit among women ages 70 to 74 years is small versus ages 60 to 69 years. “Hopefully, breast cancer treatment of the geriatric population will improve, and future studies can show that quality screening and treatment lead to a reduction in ‘overall mortality’ instead of just ‘breast cancer-specific mortality,’” the editorialist wrote.