Wednesday, February 20, 2013

Are Screening Mammograms Safe and Effective?

In 2009, I reviewed the issue of screening mammograms and supported the US Preventative Services Task Force (USPSTF) recommendation that women of average risk should start mammograms at age 50 and continue mammography every 2 years until age 75.  I have recommended mammograms with the caveat that as new information is available, I would reassess the best strategy.  New information casts further doubt as to the safety and effectiveness of mammography as a screen for breast cancer.

Let me start off by saying the obvious, we all want to reduce the rate of breast cancer.  If cancer cannot be avoided, we want to improve the outcome through earlier detection. 

Objectively thinking through the issue of breast cancer screening with mammograms is no easy task.  Screening mammograms have been promoted far more than any other diagnostic test.  Particularly in the United States, breast cancer screening is an emotionally, politically and economically charged issue.  Powerful forces are in place which put pressure on physicians and women to promote mammography but are we helping women?

The findings and conclusions of numerous studies are not at all intuitive or obvious. To digest this information, you will want to set aside what seems to be “obviously” correct and consider the facts carefully. 

What Makes For a Good Screening Test?
To understand the issue of screening mammograms, it is helpful to back up and look at what makes for a good screening test.  Screening should meet several criteria:

·       The procedure should allow early detection of cancers destined to cause death.  By diagnosing the cancers earlier - screening should be associated with better outcomes.

·       The procedure should have a high safety profile.

An effective screening approach should show early disease rates go up in an amount equal to the decline in late disease.  Effective screening tools such as Pap smears for cervical cancer and colonoscopies for colon cancer demonstrate the expected increase in early disease with a corresponding drop in late disease.  We will see this is not the case with screening mammograms.

Landmark Study
The November 22, 2012 New England Journal of Medicine landmark article “Effect of Three Decades of Screening Mammography on Breast-Cancer Incidence” by Archie Bleyer, M.D., and H. Gilbert Welch, M.D., M.P.H. looked at an enormous amount of federal data on screening mammography compiled from the mid-1970s through 2008. 

Key Study Findings
·       The rate of diagnosing breast cancer in early stages increased by 200% with screening mammography.
·       However, the rate of late stage cancer did not drop significantly in the screened group.  Metastatic disease was completely unchanged – screening did not prevent this.

This thorough review confirmed what numerous other studies have pointed to: screening mammograms do not make much of a difference in preventing late stage cancer.  They are not achieving their main goal which is to prevent cancer deaths.

Overdiagnosis of “harmless” cancer cells
You may be thinking that any chance of improvement would justify doing a mammogram.  This would be true if there were no downside to screening. While the breast cancer “overdiagnosis” problem has been discussed in the medical articles for over a decade, this issue is rarely understood and discussed even among physicians. 

While it seems obvious that it is a good thing to find cancer cells and get rid of them, the studies show this is not always so.  Our bodies often contain cancer cells that would have never effected out lives.  When we go looking for the early cancers, we often find what I am going to call harmless cancers – cancer which would never have caused disease.  We also find some of the bad cancers - destined to cause disease and potential death. 

The problem is that mammograms appear much better at diagnosing harmless cancers than early bad cancers.  Furthermore, at this time, once cancer is diagnosed there is no way to tell whether it is likely to cause disease or not.  As a result of screening mammograms, the overdiagnosis of cancer cells were found and treated in more than 1.3 million women over the past 3 decades.   In 2008, 70,000 women were overdiagnosed with breast cancer. This amounts to almost 1/3 of breast cancers diagnosed in women 40 years of age and older.  

Overdiagnosis is not benign:  These women overdiagnosed with breast cancer gained nothing by their treatment.  They would have enjoyed living their lives never being affected by breast cancer. The cancer would have never materialized as a diagnosis or health concern. 

Overdiagnosis causes overtreatment with the attendant emotional stress of the cancer diagnosis, unnecessary treatment such as surgery, radiation & chemotherapy and all the potential complications.   While treatment of early stage cancer is safer than treatment of late stage cancer, this overtreatment can sometimes cause serious complications and even death. 

The data shows 2 important problems with screening mammography:
·       Screening mammograms fail the most important criteria for screening: they fail to substantially reduce late stage disease. In fact, from 1975 to 2008 the rate of metastatic breast cancer was unchanged.

·       Screening mammography causes many women to become cancer patients who would not have been had they not been screened.

**I would want to make sure all readers recognize that all breast masses should be carefully evaluated.  The above negative findings are for screening mammograms– not diagnostic mammograms used to evaluate lumps/masses. If a woman has a breast lump/mass – it definitely should be evaluated with mammograms, ultrasound and when indicated, biopsy**

The NEJM article prompted a discussion over which of the following strategies doctors should recommend:
Option 1: Recommend Screening Mammography Starting at the Age of 40
Option 2: Recommend Screening Mammography Starting at the Age of 50
Option 3: Do Not Recommend Screening Mammography

The fact that option 3 is on the table speaks volumes.  The pressure to do screening mammograms is very intense.  For a prestigious journal to discuss this as a reasonable option reflects a large body of evidence that screening mammography has very limited benefit and significant problems.
The preponderance of the evidence we have gathered in many different countries and by many different groups show disappointing results with screening mammograms.  While the exact findings vary, women need to be aware that screening breast mammography is poor at picking up important cancers and clearly results in a great deal of overdiagnosis and overtreatment. As much as we all want a good tool to reduce breast cancer death, screening mammograms do not fill this role well. 
Should I have screening mammograms?
Since screening mammograms are not very effective or accurate, missing most important cancers and diagnosing many unimportant ones, I lean toward option 3 of not recommending mammography.  I encourage you to consider the best statistics we have and make a decision based on your assessment of the benefit versus risk:

·       We are weighing a low benefit of 0-10% in the reduction in late stage cancers

·       A significant risk of overdiagnosis.  The harm of overdiagnosis includes:
·            emotional stress
·            pain and potential complications from testing
·            complications of the cancer treatments (surgery, chemotherapy, hormonal blockers,  radiation) ranging from mild issues to severe impairment and death
·       The pain involved with screening mammograms
·       The stress of screening mammograms, waiting for the results, needing additional studies and biopsies.
·       Possible x-ray induced cancer.  X-rays involved in mammograms have a small but definite risk of causing cancers – especially when you start early and have yearly studies

This is a personal decision but the case for the often stated “screening breast mammography save lives” is much weaker than most realize.  You may choose to get screening mammograms but please do so knowing there is clear evidence that screening is associated with significant harm coming from the many cases which involve finding cancerous cells that would have never affected your life.
The Cochrane Review as a tool to make your decision
When I did medical missions overseas in Central Asia, I worked in the area of medical development with consultants with the World Health Organization (WHO) to make recommendations.  We were trying to focus on what really mattered, what really made a difference.  It was not uncommon to discuss the findings of the Cochrane Reviews. The Cochrane Review is internationally recognized as a leading source of quality evidence-based health assessments.  Because the Cochrane Review is international, it is not easily influenced by political and local economic factors.  I would urge you to consider the Cochrane Reviews’ stance on screening mammograms:
Cochrane Review 2008
·       Initially in 2008, their summary was that since mammography had both benefits and harms, either way – having it done or not having it done was reasonable.
·       At the time they estimated that if 2000 women were screened regularly for 10 years, one will benefit from the screening by avoiding dying from breast cancer.
·       At the same time, 10 healthy women would unnecessarily become cancer patients and will be treated unnecessarily. These women will have either a part of their breast or the whole breast removed and often receive radiation therapy and sometimes chemotherapy.
·       Furthermore, about 200 healthy women will experience a false alarm. The psychological strain women experience from false alarms can be severe.

Cochrane Review Revised Position
·       Since the trials used to accumulate the above statistic were performed, treatment of breast cancer has improved considerably.  When improved treatment of breast cancer is factored in, it indicates mammography screening may no longer be effective in reducing the risk of dying from breast cancer.
·       Screening produces patients with breast cancer from among healthy women who would never have developed symptoms of breast cancer. Treatment of these healthy women increases their risk of dying, e.g. from heart disease and cancer.
·       It no longer seems reasonable to recommend mammograms for breast cancer screening. In fact, by avoiding going to screening, a woman will lower her risk of getting a breast cancer diagnosis.
·       However, despite this, some women might still wish to go to screening. But women should know that screening produces patients with breast cancer from among healthy women who would never have developed symptoms of breast cancer. Treatment of these healthy women increases their risk of dying, e.g. from heart disease and cancer.

Source: Cochrane review: Screening for breast cancer with mammography   

Better Approaches
To continue to do the same thing over and over again, expecting different results, is one definition of insanity.  Moving forward, we need better tools.  Deadly cancers are routinely missed with mammograms and mammograms pick up too many unimportant cancers. 
Although clear benefit is lacking – it seems prudent to do self-breast exams as well as have your doctor perform regular breast exams.  Also, I repeat, you should definitely have a breast mass evaluated with all appropriate tools including mammograms (when done to evaluate a lump, this is called a diagnostic mammogram rather than a screening mammogram).
What might work instead of screening mammograms? Screening with ultrasound and breast thermography are promising.  However, we will only know if they really help when long term rigorous studies done on them.  Read more about breast thermography in my previous posts in the January & November 2009 blog posts. 

To your health!  
Don Ellsworth, M.D.  

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Disclaimer:  The information provided should not be construed as personal medical advice or instruction.  No action should be taken based solely on the contents of this site. Readers should consult appropriate health professionals on any matter relating to their health and well-being. The information and opinions provided here are believed to be accurate and sound, based on my best judgment and research.  I cannot assume responsibility for any possible errors or omissions.

References and further reading
Effect of Three Decades of Screening Mammography on Breast-Cancer Incidence
Archie Bleyer, M.D., and H. Gilbert Welch, M.D., M.P.H.
N Engl J Med 2012; 367:1998-2005 November 22, 2012

Cochrane Review:

Overdiagnosed: Making People Sick in the Pursuit of Health by H. Gilbert Welch, Lisa Schwartz and Steve Woloshin