STUDY SUGGESTS THAT SOME BREAST CANCERS MAY SIMPLY DISAPPEAR - PART II

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STUDY SUGGESTS THAT SOME BREAST CANCERS MAY SIMPLY DISAPPEAR - PART II

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Cancers, even advanced cancers, can sometimes undergo what is called

'spontaneous regression' - i.e., they can simply disappear without trace. A

recent

study carried out by a team of researchers led by epidemiologist H. Gilbert

Welch, MD, of Dartmouth Medical School, suggests that spontaneous regression

may be considerably more common than previously thought.

The study, published recently in the journal Archives of Internal Medicine,

followed a group of almost 110,000 Norwegian women who underwent periodic

mammographic screening for breast cancer over a five-year period between 1992

and 1997, and compared these women with a second, matched group of women who

did not undergo regular routine breast cancer screening during the same period.

Surprisingly, the women who underwent regular screening had 22 percent more

invasive breast cancers than those who did not (Zahl, 2008).

The publication of the study was considered sufficiently important to merit

an accompanying editorial in Archives of Internal Medicine. The authors of

the editorial point out that it will be impossible to verify whether or not the

22 percent difference in breast cancer diagnoses between screened and

unscreened women is indeed due to spontaneous regression of breast cancers

unless a

full-scale clinical trial is performed. That said, it would probably never

be possible to conduct such a clinical trial since it would be considered

unethical to leave one group of women untreated. " Despite the appeal of early

detection of breast cancer, " wrote the editorialists, " uncertainty about the

value of mammography continues. "

This study is not the first to raise troubling questions about the natural

history of certain breast cancers and the risks versus the benefits of

screening mammography. For example, an earlier study carried out in Canada in

2002

also found an identical 22 percent difference in cancer diagnoses between

women who went unscreened and those given regular mammograms (Miller,2004) .

Another study, this one published in the prestigious British Medical Journal in

2004, reported similar rates of over-diagnosis, concluding:

" Without screening, one third of all invasive breast cancers in the age

group 50-69 years would not have been detected in the patients’ lifetime.

This

level of over-diagnosis is larger than previously thought " (Zahl, 2004).

 

SCREENING FOR BREAST CANCER: RETHINKING THE ACCEPTED PARADIGM

 

 

There is no doubt that when detected in its early stages, breast cancer is

very often curable in the truest sense of that word, and screening mammography

may be useful as a component of an early detection program. But as with any

medical procedure, there are risks as well as benefits to screening for

cancer, and the possibility of over-diagnosis leading to unnecessary treatment

is

an inherent drawback.

Undoubtedly, the study will cause considerable controversy. Already, Robert

A. Smith, director of breast cancer screening at the American Cancer Society

(ACS), has commented in a surprisingly intemperate way on the study: " Their

[the study’s authors, ed.] simplification of a complicated issue is both

overreaching and alarming, " he told the New York Times. The ACS has long been a

staunch promoter of screening mammography.

Yet the design of the latest study was indisputably an ingenious one, and

the findings demand further investigation. The purpose of the study was to

quantify the potential size of the over-diagnosis/over-treatment problem - a

problem that even proponents of screening mammography acknowledge exists. In

their conclusions, the authors take pains to point out that their aim was not to

discredit the use of mammography in screening for breast cancer.

" It is also important, " they write, " to emphasize that our findings have no

bearing on the debate on whether screening mammography reduces breast cancer

mortality. Our findings are equally consistent with the possibility that

mammography either leads to a reduction in breast cancer mortality or has no

effect at all. Instead, our findings simply provide new insight on what is

arguably the major harm associated with mammographic screening, namely, the

detection and treatment of cancers that would otherwise regress. "

Another important consideration (and one that the Archives of Internal

Medicine study was not designed to address) is the contribution of radiation

exposure from repeated mammograms to the overall incidence of breast cancer.

Despite emphatic assurances concerning the safety of mammography, it is

acknowledged by experts that the procedure (like all exposure to ionizing rays)

does

somewhat heighten the risk of radiation-induced cancer. This is particularly so

when a mammogram has to be repeated because of questionable readings. The

danger begins to add up when hundreds of thousands of women are being screened

annually. The risk of radiation-induced cancer needs to be taken into account

in making the decision as to when to begin regular screening mammography.

There is no doubt that every life saved is something to celebrate. But there

is legitimate cause for concern that a significant number of women are being

treated unnecessarily for abnormalities that might never have become

clinically apparent or represented any threat to life. The onus is now on the

cancer

research community and the medical profession to look long and hard at the

basic assumptions underlying the wide-scale adoption of mammographic screening

programs. After all, if one could identify in advance which tumors are

likely to progress to cancer, and which are just a temporary aberration, a great

many women could be spared the ravages of aggressive treatment.

 

 

 

--Ralph W. Moss, Ph.D.

References:

Everson, Tilden C and Cole, Warren Henry. Spontaneous regression of cancer;

a study and abstract of reports in the world medical literature and of

personal communications concerning spontaneous regression of malignant disease.

Philadelphia, Saunders, 1966.

Kolata G. Study suggests some cancers may go away. New York Times Nov 25

2008.

Miller AB, To T, Baines CJ, et al. The Canadian National Breast Screening

Study-1: breast cancer mortality after 11 to 16 years of follow-up. A

randomized screening trial of mammography in women age 40 to 49 years. Ann

Intern Med

2002;137(5 Part 1):305-12.

Mulcahy N. Mammography study suggests some breast cancer may spontaneously

regress. Medscape Medical News Nov 25 2008, accessed at:

_http:// www.medscape.com/viewarticle/584147_

(http://%20www.medscape.com/viewarticle/584147) (subscription required).

Zahl P-H, Maehlen J, Welch, HG. The Natural history of invasive breast

cancers detected by screening mammography. Arch Intern Med.

2008;168(21):2311-2316.

Zahl P-H, Strand BH, Maehlen J. Incidence of breast cancer in Norway and

Sweden during introduction of nationwide screening: prospective cohort study.

BMJ 2004;328(7445):921-4.