Study observes reduced benefits of breast cancer screenings

A new study found that the effect of breast cancer screenings is declining as the cost and problems surrounding screenings, including overdiagnosis and overtreatment of the cancer, are either fixed or increasing, possibly outweighing the benefits.

The study, published in the European Journal of Public Health, and led by Soren Christiansen, MPH, of the department of public health at Aarhus University in Denmark. According to the study, there are both benefits and harms to breast cancer screenings. Along with preventing severe infection, breast cancer screenings can also lead to overdiagnosis and overtreatment of the disease. For this study, researchers aimed to quantify the benefit-harm balance of breast cancer screenings.

The study’s researchers began by estimating the individuals needed to invite for a screening to prevent one breast cancer death within 10 years. Researchers analyzed data on 10,580 Norwegian and Danish women aged 50 to 70 collected between 1986 and 2016. Four scenarios of screening effectiveness were applied to the data in addition to three scenarios of overdiagnosis to estimate ratios of overdiagnosis and breast cancer deaths prevented.

In the beginning of the study, researchers estimated that breast screenings prevented 20 percent of breast cancer deaths and that 20 percent of the screenings resulted in overdiagnosis. From 1996 to 2016, the number of women invited for a screening increased from 731 individuals to 1,364. During that same period, the percentage of overdiagnoses remained fixed showing that one in every five women were misdiagnosed with breast cancer. In contrast, there was a breast cancer mortality ratio rose from 12.8 in 1996 to 25.2 in 2016. The number of women over diagnosed with breast cancer rose from 3.2 in 1996 to 5.4 in 2016.

According to the author, these results suggest that not only the financial cost, but also the cost associated with overdiagnosis and overtreatment, could outweigh the benefits of these cancer screenings which may not be necessary with the level of advancements in treatments.

"The beneficial effect of screening is currently declining because the treatment of cancer is improving,” said Henrik Støvring, of the department of public health at Aarhus University, and one of the study’s researchers in a statement. Over the last 25 years, the mortality rate for breast cancer has been virtually halved.”