Mammograms: Are they needed or not?

CNN/ Newswire | 2/19/2014, 9:33 a.m.
The subject of breast cancer screening is often in the news as ongoing clinical studies publish updates and experts debate ...
The consensus is that mammograms are beneficial for women 40 to 75.

By Dr. Otis Brawley

CNN contributor

The subject of breast cancer screening is often in the news as ongoing clinical studies publish updates and experts debate the merits of the findings.

Breast cancer is an emotional issue because it kills thousands of women per year. Many are in the prime of their lives.

There seems to be conflicting messages regarding screening, so I can understand how it can be confusing to the layman. I have been a cancer screening expert for more than two decades, and the headlines are often confusing to me. Perhaps I can bring some clarity to the issue.

Mammography (breast X-ray) was developed in the 1950s. The concept of using it to search for early cancer came about soon thereafter.

Does breast screening save lives?

Simply finding cancer is not proof of a test's benefit. One must find the cancer, provide treatment and demonstrate that patients who would have died do not. Several screening tests for other cancers have been found not just useless but also harmful because the nature of the cancer was that early detection and treatment did not save lives.

The best way to determine whether a breast screening test is beneficial is through a prospective randomized study in which women are enrolled and randomly assigned to be screened or not, then followed over time. The goal is to determine that there are less breast cancer deaths in the heavily screened group.

A number of these clinical trials have and are being conducted in North America and Europe. The earliest began in 1963. The last began in Europe and Canada in the 1980s. Unfortunately, no study is perfect; each has flaws.

These studies are huge and follow women for decades. The smallest enrolled 45,000 women and the largest more than 160,000. The studies are logistical challenges; some have even reported different numbers of women enrolled in different publications.

The studies ask different questions. Most studied women 50 and older. Only two were designed to look at women 40 to 49. Some asked whether mammography is better than no screening. Some studied whether screening with mammography and clinical breast examination is better than clinical breast examination.

When looking at these trials in 2014, there are challenges common to every study:

• First, some women in the "do not screen" group began getting screened as initial reports of some studies showed a benefit to screening. The studies began assessing the long-term outcomes of groups of women who had been intensively screened over the years versus groups lightly screened over the past decades.

• The quality of the mammography equipment has improved such that all the studies available used what is now obsolete imaging equipment.

• Treatment of breast cancer has improved. Early detection may be less important today than two decades ago.

These are the studies we have to make decisions from. It is unethical to start new studies because the consensus is that screening has some benefit; we cannot randomize women to the nonscreening arm of a new trial.