Foreground Questions: Does Early Detection of Cancer Save Lives?

In the April 6 issue of Newsweek, columnist Sharon Begley discusses the myth, propagated my medical science and eager health consumers, that early detection of cancer saves lives.  It would seem to make sense, wouldn't it, that detecting cancer early saves lives, but there is little evidence to support the notion. 

In her column, Begley refers in broad narrative format to the following specific underlying questions:

Q:  Do men who are screened for prostate cancer with the screening test called PSA, or prostate specific antigen, have a reduce rate of death from prostate cancer compared to those who are not screened?

A: Yes, but by only a tiny amount.  Because there is only a risk difference (absolute risk reduction) between the two groups of 0.71 percent, that means that 1410 men would have to be screened in order to prevent one death from prostate cancer (number needed to screen).  This does not consider all-cause mortality.

Source:  N Engl J Med. 2009 Mar 26;360(13):1320-8. Epub 2009 Mar 18.

Q: Do male smokers who are screened for lung cancer with sputum samples and chest X-rays every 4 months have a lower risk of death from lung cancer than male smokers who are not screened?

A: No.  The risk difference (absolute risk reduction) between the two groups is only 0.5 percent; that means that 200 male smokers would have to be screened in order to prevent one death from lung cancer (number needed to screen), if we had confidence in the results. Because the results of the study had wide confidence intervals, the difference is considered to be not statistically significant, and is described as no difference. 

Source: JNCI 2000 Aug 16;92(16):1308-1316

Q: Do women under age 50 who are screend for breast cancer with mammograms every year have a lower risk of death from breast cancer than women who do not get annual mammography screening exams?

A: Yes, but only by a tiny amount.  The risk difference (absolute risk reduction) between the two groups is 0.04 percent; that means that 2,500 women under age 50 would have to be screened in order to prevent one death from breast cancer. 

Source: Lancet 2006 Dec 9; 368(9552) 2053-60

Addendum 11/17/09: The smart people at the US Preventive Services Task Force (part of the Agency for Healthcare Research and Quality) have changed mammogram recommendations to start at age 50, and then only every two years. 

But remember: screening mammograms may be indicated earlier in people who have a higher baseline risk of breast cancer (like women whose mother or sister has had breast cancer).  And mammograms for people who have symtpoms are a different case altogether.  Consult your own doctor to understand your personal risk-benefit profile for mammograms. 

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Barbara Lock
Posts: 3

Number Needed to Screen
Reply #3 on : Wed November 18, 2009, 07:37:58

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I believe that the NNS of 1 in 2500 actually referred to women under 40 who were screened annually for ten years, not 1 in 2500 individual mammograms.

What we need to better understand this information is knowledge of how many cancers are diagnosed in women under 40 who are screened for 10 years. It will be far greater than 1 in 2500, indicating that either 1) many would have regressed on their own with out treatment or 2) something about the screening intervention and treatment adds to the risk of death compared to starting screening later.

I have had several friends with breast cancer, including one who died, but who would not have benefited from a mammogram because the aggressive type of cancer she had is not detectable on a mammogram, and one who nonchalantly called her cancer "pee wee cancer," understanding that since it was caught so early, it might very well have been one of those cancers that would have disappeared on its own.

Kathy Werblow
Posts: 3

Breast Cancer
Reply #2 on : Tue November 17, 2009, 23:55:10

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So, 2,500 women under age 50 need to have a mammogram to save one woman. That still adds up to a lot of women dying if we all half to wait until we are 50 to have our first mammogram. I was diagnosed at age 45. I had absolutely no history of cancer of any kind in my family! My tumor was deep, so that it couldn't be felt manually. Had I not had a regular screening mammogram my cancer would have spread and would probably have been terminal by the time it was diagnosed. Cancer is younger women (under 50) tends to be more aggressive. But I guess my life isn't worth the price of 2500 mammograms? At least not according to this study. This is all about saving greedy insurance companies money.

Maggie
Posts: 3

Mammograms
Reply #1 on : Tue November 17, 2009, 21:54:18

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It is a way for the government to cut down on costs. This is the beginning of VERY LIMITED health care, IF this bill is passed. No only on the subject of Mammograms, but EVERY test that the, so called committee, that the government chooses to make Medical judgement on your LIFE!
It doesn't matter to them when you die, just how long you will be an expense to the government. Therefore, you will be given ONLY what they tell you,you can have, whether your doctor agrees or not.

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