We are on a search for truth, but will we ever find it? That summarizes how I feel after reading an article in the New England Journal of Medicine, which once again raises the question of how much screening mammography contributes to the progress we have made in reducing deaths from breast cancer in the United States, and by inference, in other parts of the world.

The research paper-written by Dr. Gilbert Welch and Dr. Archie Bleyer, two highly regarded researchers-concludes that over the past 30+ years, screening mammography has contributed modestly, at best, in the progress we have made in decreasing death rates from breast cancer.  In contrast, based on their analyses, the doctors conclude that much of the gains we have seen are due to better treatment. An additional observation is that 31 percent of the women diagnosed and treated for breast cancer in 2008 – that’s more than 70,000 women – were in fact treated unnecessarily, since if left alone or not diagnosed their cancers would never have caused them a problem during their lifetime. In contrast, they say, these women have endured surgery, perhaps radiation and chemotherapy, all of which have serious consequences and in fact did not contribute to their health or their longevity.

This is not the first research that has been done on this very important-and very emotional–topic nor is this the first time that the question of “over diagnosis” and “over treatment” of breast cancer has become part of the national debate over the value of early detection of breast cancer.

As the authors acknowledge, there has been a considerable body of research that has tried to answer the question regarding the value of mammography, and assess the “harms” of screening mammograms (which, for the patient may include repeat examinations such as additional mammograms, ultrasound and MRI, and for some women, breast biopsy in order to determine whether or not a suspicious lesion is in fact cancer). There have also been a number of studies-some of which are included in an online table which accompanies the Welch and Bleyer report-which try to determine how many women were treated for their breast cancer without health benefit.

So let’s acknowledge two basic principles:

One: Many experts agree with the principles espoused in this current report. Yes, some women do have to undergo additional studies to determine if something seen on a screening mammogram is in fact a cancer.

Two: many experts acknowledge that we do treat some women who would otherwise have done perfectly well had we not found their breast cancers in the first place.

Where we disagree on that question is whether the correct percentage is 31 percent as suggested by the authors, or somewhere else in the range of published numbers, which varies from about 5 percent all the way up to 50 percent.

Let me also acknowledge the following:

The American Cancer Society continues to follow the scientific literature on this topic carefully. As of today, we continue to recommend women at average risk for breast cancer should have a screening mammogram every year beginning at age 40, along with a clinical breast exam.

What frequently gets “lost in the sauce” is that we also acknowledge the concerns that have been raised regarding the matter of over diagnosis and the benefits, risks and harms of screening mammograms. These are important, and women should be fully informed as they make a decision about what is right for them.

Yes, we obviously believe screening should begin at age 40, but unlike some recent media reports suggest, we do realize that other respected experts do not agree with us.

As I look back at the history of this issue, I can’t ignore some personal knowledge and experience.

When I started medical school in the late 1960’s, we were told right from the beginning that there were cancers found on autopsy that never presented a problem during a person’s lifetime. The most common cancers in this category were breast, prostate and thyroid, but there were others as well.

Cancer back then was (and still is) a very serious disease. In 1977 when I started my practice in medical oncology, there was still considerable debate about screening mammography, but it was starting to take hold in a number of communities around the country. The reality was that many women presented when they felt a lump, and only found out they had had breast cancer after surgery, when they woke up from anesthesia without a breast and with a very disfigured chest.

Research at that time showed that many cancers were about an inch in size or larger, while almost half of the patients had lymph nodes involved with cancer-which research showed us actually was a marker for more disseminated disease throughout the body. Thus, the efforts beginning around that time to develop chemotherapy strategies to reduce the risk of cancer recurrence, and other studies to prove that we could do less disfiguring surgery and leave women with a more satisfactory cosmetic result following treatment.

We were guilty then of believing that mammography was an answer to our prayers. We did believe that finding every cancer earlier was a good thing. We did believe that smaller cancers and lesser surgery would encourage more women to become more aware of breast cancer and come to us sooner for treatment which had a much higher probability of curing the disease than was the case at that time.

We learned along the way that mammography wasn’t perfect. Mammography doesn’t find every cancer early. Even breast cancers detected early can spread later on. Screening mammograms were not an “all or nothing” answer to reducing deaths from breast cancer.

But I would maintain-as hopefully would others-that research has shown us that mammography does save lives. Maybe not enough lives in some age groups to satisfy some people, but it does save lives. And I would maintain that it is very difficult-again, as shown by data in a number of research studies-to precisely “parse out” what contribution mammography makes in reducing deaths from breast cancer vs. the increased awareness of women regarding breast cancer (i.e., October’s Breast Cancer Awareness Month with the pinking of the world) vs. improved adjuvant therapy.

What we do know is that beginning in the early 1990’s we started to see what has turned out to be an ongoing decline in deaths from breast cancer. Perhaps not as great an impact in some ethnic communities as others, but a reduction nonetheless. We could argue how much each factor contributes to that result, but we can’t ignore the result.

We also can’t ignore the fact that our mammography technology has continuously improved. We can now find very small cancers in the breast. That means a greater proportion of those cancers are going to be the type that my anatomy professors pointed out in the 60’s. What we can’t do with as much accuracy as we would like for more women with breast cancer is to determine which ones are going to be lethal and which ones can be left alone. We will get there, I believe, probably through our advances in understanding the genetics of cancers. But we are not there yet.

Which leaves us on the horns of a dilemma: if the message of today is that we “over treat” women, the question remains “which ones?” And truth be told, we can’t answer that with a high degree of accuracy. So we are left with a problem that does not have a precise answer. The researchers in their report estimate 1.3 million women have been treated “unnecessarily” for breast cancer, but I defy them to scientifically tell a woman whether or not she was one of those who were “over treated.”

We live in a headline driven world. The role of mammography for women is not immune to that influence. There will be many, many headlines on this topic, but too few folks will actually read the body of the article. And there is no telling how the body of any particular media article is going to portray the story, whether it be written to scare women or provide them with accurate information.

There is no way to tell how women are going to make up their minds to get screened or not get screened for breast cancer, but I can bet you there are going to be some who see the headlines and decide that mammography is not for them. Unfortunately, the researchers can’t tell them whether or not they made the right decision for themselves as an individual. We just don’t have the science to answer that question for any individual woman. So it comes down to basic facts: until science supplies us with the accurate answer, each woman has to make a decision regarding screening mammography. Hopefully that decision will be an informed one through discussion with a knowledgeable health professional in conjunction with reliable information available from other sources (such as the American Cancer Society at  www.cancer.org).

Many of us are concerned that women will read or hear the headline and forego screening mammograms altogether. We at the American Cancer Society-and I suspect many other experts-do not believe that would be the right approach. At least pick a suggested screening program that is right for you. We would recommend our guidelines, but we recognize there are others.

But at the end of the day, do not believe that the message delivered today is the end of the discussion. It is not. There was a different message delivered in other research papers last month, as there have in years past and will be in years to come until we get the scientific answers and guidance we need.

The search for the truth must continue unabated. Too many lives depend on it.

J. Leonard Lichtenfeld is deputy Chief Medical Officer for the national office of the American Cancer Society. He blogs at Dr. Len’s Cancer Blog.