A Closer Examination of Screening Mammography

Recently, mammography, specifically screening mammography, is falling under scrutiny in the scientific and medical community.  As we are aware, mammography is utilized as a screening tool on an annual basis for otherwise healthy women to monitor for any evidence of cancer. 

A second way mammography is used is in a diagnostic mode.  If a woman has a detectable lump, mammography has proven to be effective in detection and ruling-out or ruling-in evidence for exiting disease. 

It is the debate of the effectiveness of mammography as a screening device that is causing controversy.  In this month’s newsletter, we explore this controversial subject.

We begin screening mammography usually around the age of 40 with the belief that “early detection” is the key to the best prognosis for survival.  So let’s ask a few questions:

1.  If screening mammography is recommended at age 40, what is the real benefit for this young population of women?

The benefit for the younger women, aged 40-49 is actually less than 1% reduction in absolute risk.  The data show that the real benefit for number of lives saved by annual mammographic breast screening actually is in women aged 50-74.  This data was first reported in 2009 when the US Preventive Services Task Force performed a meta-analysis.  The results led them to recommend mammography beginning at age 50 and then alternating years up till age 74.  Mammography was not recommended after age 74.

Some medical doctors still recommend annual screening mammography beginning at age 40.

2.  If “early detection” increases survival, does screening mammography find cancers at “early” stages of development?

All breast cancers are NOT the same in how fast they grow and what stimulates them to grow.  According Donald Berry, PhD and chairman of the Department of Biostatistics and Applied Mathematics at M. D. Anderson Cancer Center (Houston, TX), technology has brought a new understanding to the different types of breast cancers and can be best-described in the following manner:

a. Turtles
Some breast cancers are non-progressive, very slow-growing tumors and sometimes characterized as “stationary” tumors.  Breast cancers that are described as “turtles” could be found by either breast self exam or clinical breast exam and because of their slow-growing nature could be treated successfully without annual mammograms.  Women with this type would not necessarily benefit from annual mammographic screenings.

b. Bears
These types of breast cancers are sometimes hibernating or slow-moving tumors. At times they may show no aggression or advancement.  However, if awakened, this type can become aggressive, spread and potentially lead to metastatic disease and death.  There is a possibility that women with this type could be helped by screenings.

Of course, breast density needs to be part of the equation to determine if a woman would benefit from annual mammograms since mammograms are limited by the density of breast tissue.  The denser the tissue, the more difficult it would be for a tumor to be seen.

c. Birds
Characterized as fast-growing, aggressive tumors these types of breast cancers do not respond to treatment, no matter how small the tumor is when found.  Early detection would not play a role in survival as these aggressive tumors develop quickly and no current medical intervention leads to survival.  Sadly, women with this type would also not be helped by screening mammography because the end result would be the same.

Although we now know about the different types of breast cancers, researchers still cannot distinguish between the different types of breast cancers in how they behave.

Statistics show that mammography most effectively detects the slow growing tumors that would be treated successfully regardless of when and how they are found. 

Additionally, pathologists grade cancer cell aggression according to the “mitotic count”— the rate at which the cells are dividing, not the size of the tumor when detected.  Below is a simple study that clearly defines these facts:

Pathologist Peggy Porter analyzed four hundred and twenty-nine (429) breast cancers that had been diagnosed over five years at the Group Health Cooperative of Puget Sound:

• 279 breast cancers were detected by mammography
• Majority detected at Stage 1
• 18% with lymph node involvement
• 70% of the 279 tumors had “low” mitotic counts

Further analysis of the findings indicated the following:

• 150 cancers were missed by mammography
• Majority were in Stage 3
• 28% with lymph node involvement
• Three-times more likely to have “high” mitotic counts

The majority of the undetected breast cancers didn’t exist at the time of the mammogram. These cancers were found in women who had had regular mammograms, and who were legitimately told that they showed no sign of cancer on their last visit. In the interval between X-rays, however, either they or their doctor had manually discovered a lump in their breast.  These tumors were so aggressive that they had gone from undetectable to detectable in the interval between two mammograms.

Although the above study is small, the findings with mammography continue to be the same and this is the reason it is now questioned as an effective screening tool for breast cancer.

Also, screening mammography has not changed the rate women are diagnosed with late stage cancer or metastatic breast cancer.  The decreased rate of death from breast cancer is not due to the screening method but rather, the treatments available. 

Screening mammography is finding tumors that may not be lethal and creating “over diagnosis” leading to over treatment.  Because doctors cannot distinguish between the different types of breast tumors most cases will lead to surgery and possibly radiation and chemotherapy or hormone therapy.  Thus, some women are receiving unnecessary treatment that is not beneficial yet carries toxic and significant side effects.

The “war on cancer” began back in the 1970’s when it was believed that tumor size was directly related to survivability.  It was this understanding that may have fed the idea that annual mammographic screening could lead to early detection and the familiar mantra, “early detection saves lives.”

Science and technology has a greater understanding that it is the behavior of cancer (Turtle, Bear or Bird) that plays a role in survival, not the size of the tumor.  And therefore, for all these reasons above, the use of mammography as a screening tool is questioned. 

As Level III Clinical Thermographers, we ask ourselves what role thermography may play in these findings.  Please look for your April newsletter to discuss this next topic. 

Yours in prevention,
Brenda and Lynda

Sources:  The Picture Problem: mammography, air power and the limits of looking - Malcolm Gladwell

The Oversimplification of Early Detection: Screening Mammography and Breast Cancer Overdiagnosis – Breast Cancer Action (online presentation – March 12, 2013)