THE MOSS REPORTS Newsletter (10/16/05)

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THE MOSS REPORTS Newsletter (10/16/05)

 

 

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Ralph W. Moss, Ph.D. Weekly CancerDecisions.com

Newsletter #206 10/16/05

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THE MOSS REPORTS CANCER DECISIONS NEWSLETTER

 

 

It is a modern day mantra, endlessly repeated and unquestioningly

accepted, that screening for cancer offers the best chance of early

detection and therefore saves lives. But is this really true?

 

Last week I began a discussion of the rationale for, and the scientific

basis of, screening mammography. That discussion continues this week.

 

To read this week's newsletter, please click or go to:

http://www.cancerdecisions.com/101605.html

 

 

MAMMOGRAPHY – THE HIDDEN DOWNSIDE, PART TWO

 

 

Last week I began a discussion of mammography. That discussion

continues this week.

 

Mammography Does Not Predict Cure

 

 

Before a breast malignancy becomes detectable by mammography it has

typically been present for 8 years.

 

It is also worth remembering that simply because a tumor is detected

by mammography does not necessarily mean that it will be cured. For

example, half of the breast cancer deaths recorded in two important

Swedish studies of screening were among women whose tumors had first

been discovered by mammography (Duffy 1991).

 

Consider this: while 6 out of 1,000 50-year old women may die in the

next 10 years if they do not have mammography, as many as 4 in 1,000

will still die even though they have had regular mammograms. The

benefit conferred by mammography for this group of 1,000 women

therefore works out to just 2 lives saved over a period of 10 years.

 

Mammography is also not very sensitive, particularly for younger

women. In younger women the breast tissue tends to be denser than it

is in postmenopausal women, making the recorded film image much more

difficult to interpret. This in turn can lead to an increased

likelihood of misinterpretation of the radiographic image. The same is

true of a substantial proportion of postmenopausal women who are

taking estrogen supplements or hormone replacement therapy. These

supplements can increase breast density, making mammograms just as

hard to read as those of younger women with dense breast tissue.

 

The advent of digital mammography, in which the traditional X-ray film

is replaced by a digitized, computer-enhanced image of the breast, may

make the imaging of denser breast tissue more accurate, and according

to a study published in the New England Journal of Medicine in

September 2005 this technique has already shown itself to be better

than traditional film mammography at identifying suspicious lesions in

women with radiographically dense breast tissue (Pisano 2005).

 

Mammography has a high false positive rate – that is, an area may be

labeled suspicious, and further tests, including biopsy (the removal

and examination of a sample of tissue for diagnostic purposes), may be

initiated, only to find that it was a false alarm, and there is no

abnormality. Mammography, in other words, is by no means fail-safe,

and over time, a very significant number of women who undergo

mammography will experience at least one false positive test. One

study found that if 32 million American women aged 40 to 79 years old

received breast cancer screening annually for 10 years, 16 million of

those women would have at least one false positive mammogram – i.e.,

the chance of a woman receiving a false positive test over 10 years of

regular mammography is around 60 percent (Elmore1998).

 

If you have ever been through one or more of these " false alarms " you

will know the psychological harm that they do. Your life, and often

that of your entire family, is put in abeyance, as you hold your

breath awaiting the verdict of the radiologists and pathologists in

your case. This agony can go on for weeks.

 

The chance of a false positive is compounded by the human factor: all

mammograms must be 'read' (i.e., interpreted) by a radiologist, and

for many reasons (not least the fear of litigation) a radiologist may

err on the side of over-diagnosis, thus adding to the probability of a

false positive reading. In one study, for example, almost 60 percent

of responding radiologists reported that their awareness of the

potential for lawsuits moderately to greatly increased the number of

their recommendations for further tests, including breast biopsies

(Elmore 2005).

 

Abnormal mammograms are far more common in the US than elsewhere in

the world: approximately 11 percent of all mammograms are declared

abnormal in the US versus only 2 to 5 percent in Europe. This is not

because breast abnormalities are more common in the US than elsewhere,

but because there is a marked tendency to over-diagnose breast cancer

in this country.

 

Furthermore, skill at reading mammograms varies widely depending on

the particular setting in which the mammogram is performed. In the

best teaching hospitals and large cancer centers radiologists may well

come up to higher standards of excellence than they do in the setting

of community health and screening centers. A 2002 New York Times

article on this subject exposed some alarming disparities between the

two settings (Moss 2002).