Risks and Benefits of Mammography Screening - Harding Center for Risk Literacy

Background:

Facts Boxes…
communicate the best available evidence about a specific topic in an easily understandable manner. The most important pros and cons are contrasted with each other in a table, thus allowing even people with no medical or statistical background to make competent decisions.

The idea…
of Facts Boxes was developed by Lisa Schwartz and Steven Woloshin. They could demonstrate in several studies that the general public could be successfully informed about harms and benefits of medical treatments via facts boxes.

Sources:
Schwartz LM, Woloshin S, Welch HG. (2007). The drug facts box: providing consumers with simple tabular data on drug benefit and harm. Med Decis Making 27:655-62.
Schwartz LM, Woloshin S, & Welch HG. (2009). Using a drug facts box to communicate drug benefits and harms: two randomized trials. Ann Intern Med 150:516-27.

Risks and Benefits of Mammography Screening

Screening for breast cancer with mammography is offered to older women at no cost by health insurance in many countries. Mammography is an x-ray examination of the human breast and aims to increase the chance of recovery by detecting existing tumors as early as possible. But what is the actual benefit of mammography screening and how frequent are potential harms? And would participating in the screening be advisable for you?

Medical questions often have no black-and-white answers. For this reason, transparent information is crucial - as is the courage to make informed decisions oneself. To help you weigh the pros and cons of mammography screening, we have prepared a facts box with neutral and easy-to-understand information about its harms and benefits.

The numbers refer to 2,000 women over 50 years of age* who participated in the screening for 10 years (screening group), compared to 2,000 women of the same age who did not participate in the screening during the same time period (control group).

factbox_mammography

The facts box shows that mammography screening reduced the number of deaths through breast cancer from 8 to 7 in 2,000 women. This effect had no influence on all-cancer mortality: The number of women who died of any cancer was the same in both groups.

200 of 2,000 women in the screening group had at least one suspicious screening result within the 10 years, though it later proved to be a false alarm. Some of these women had to live with this uncertainty for months and had to go through further diagnostic testing until the all-clear could be given.

Mammography screening also detects so-called "indolent" (slowly growing or less aggressive) tumors, which would never develop into a life-threatening disease. But because their development cannot be predicted, about 10 of 2,000 women in the screening group had their breast completely or partially removed, though this would not have been necessary.

Unfortunately, there are few good studies to date that have investigated mammography screening. The numbers in our fact box are taken from a systematic review of these studies and hence are the best evidence available. Nevertheless, the numbers should not be interpreted as definitive but instead as roughly conveying the extent of possible benefits and harms.

* The numbers for breast cancer mortality refer to women above 50 years of age. Because other data are not available, all further data are based on studies that also included women above 40 years of age.

Source:
Gøtzsche PC, Nielsen M. Screening for breast cancer with mammography. Cochrane Database of Systematic Reviews 2011, Issue 1. Art. No.: CD001877. DOI: 10.1002/14651858.CD001877.pub4
>> plain language summary of the study on Cochrane.org