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2 good choices to prevent breast cancer
I - BREAST CANCER  RISK FACTORS	II - SCREENING X-RAY MAMMOGRAPHY		III - ALTERNATIVE TESTS
▪ The biggest risk factor ▪ Risk factors overview ▪ Times change	END OF A MYTH ▪ The whistle ▪ Contra-argument ▪ Last decade ▪ Current picture		OTHER  X-RAY TESTS ▪ Digital standard ▪ Tomosynthesis ▪ Breast CT
Predisposing factors ▪ Diet      ▪ Other	BENEFIT ▪ Earlier diagnosis ▪ Fewer breast cancer deaths		Gamma-ray tests ▪ BSGI/MBI  ▪ PEM
INITIATING  FACTORS ▪ Radiation ▪ Chemicals ▪ Viruses
	RISK  &  HARM		OTHER  TESTS ▪ Breast MRI ▪ Ultrasound ▪ Thermography ▪ AMAS test
	INACCURACY RISKS	▪ False negative ▪ False positive ▪ Overdiagnosis
PROMOTING  FACTORS ▪ Hormonal ▪ Non-hormonal	RADIATION	▪ Radiation primer ▪ Screen exposure ▪ Radiation risk
			PHYSICAL EXAM ▪ Clinical ▪ Self-exam
	▪ Higher all-cause mortality?
• Minimizing breast cancer risk

It is 16 years now since Lancet published a study by two Canadian researchers, attempting to give a rational, balanced account of what available research data says X-ray mammography does, and doesn't (Wright and Mueller, Screening mammography and public health policy: the need for perspective, 1995). The authors concluded that

the facts do not support public funding for mammographic
breast cancer screening.

The reason? As table below shows, they found that only the first two, out of six large randomized controlled trials at the time, have come up with statistically significant reduction in mortality from breast cancer in study populations screened by mammography: 23% and 31% in the New York and one of the Swedish studies (Two-County), respectively (for the relative mortality reduction, corresponding absolute mortality reduction figures were much lower, 0.05% and 0.14%, respectively).
 

BREAST CANCER SCREENING TRIALS REVIEW, Wright and Muller 1995
TRIAL/DATA		End year	Duration (years)	Women in screening group	Breast cancer deaths		Ratio S/C	Statist. signif.1	Women to screen for 1 less death
					screen	control
New Yorka		1982	10	31,881	147	192	0.77	yes	7,086
Swedish Two-Countyb		1985	7	78,085	87	127*	0.69	yes	13,665
Malmoc		1988	9	21,088	63	66	0.95	no	63,264
Edinburghd		1990	7	23,226	68	76	0.89	no	20,322
Stockholme		1991	7.4	40,318	39	58*	0.67	no	15,783
Canadaf	40-49y	1992	8	25,214	38	28	1.36	no	(20,171)2
	50-59y			19,640	38	39	0.97	no	157,120
	total			44,854	76	67	1.13	no	(39,870)2

a Shapiro et al.  Ten to fourteen year effects of breast cancer screening on mortality
b Tabar et al.  Reduction in mortality from breast cancer after mass screening with mammography
c Andersson et al.  Mammographic screening and mortality from breast cancer: the Malmo Mammographic Screening Trial
d Roberts et al.  Edinburgh trial of screening for breast cancer: mortality at 7 years
e Frisell et al.  Randomised study of mammography screening - preliminary report on mortality in the Stockholm trial
f Miller et al.  Canadian National Breast Screening Study
--
1 "Statistically significant" is determined by a sufficient statistical probability of an outcome not to be result of a chance
2 Women to screen for 1 death added (the women to screen averages for the Canadian trial are not given in the study)
*Adjusted for the difference in group sizes

Note that Wright and Muller did not include Göteborg trial (started in 1982, ended 1990), possibly because complete data hasn't been published at the time (nor, for that matter, was as of 2009).

In the three trials following the New York and Two-County, mortality reduction in mammography groups was statistically insignificant, and in the last one the mammography group had higher mortality (though also statistically insignificant) than control.

To illustrate the risks and benefits, the authors made a simple calculation. The number of women needed to screen for 1 breast cancer death less ranged from 7086 to 63,264 in the five studies with mortality reduction, averaging 24,000. Combining it with the study that showed mortality increase for the mammography cohort, it comes to

1 breast cancer death less for every 32,000 women screened.

At the then-published rates, that one death less would come at the price of roughly 1,500 false positives, 4,000 false negatives, and $2 million spent on screening (note that the authors in their paper left out the Canadian study with its negative mortality effect, and used a rounded off number of screenings for 1 death less in 20,000 screened women, but it doesn't change the big picture).

In short, statistical benefit of mammography screening, as indicated by these six studies, is so small that

can be qualified as uncertain.

What is certain, are the harms caused by test's inaccuracy, its cost, and its radiation risk, which may be significant for highly sensitive women.

If so - and the evidence does support such conclusion - the huge amount of money spent on mammography and related procedures, could be used more efficiently (i.e. on some other forms of diagnostic test, and/or preventive treatments) to combat breast cancer.

Despite being fundamentally correct, the study made no impact. Nothing seemed to have the power to disturb the mammography doctrine. Instead, life-saving "benefits" of mammography screening were to be extended to women below age 50.

If Wright and Mueller stirred any change, it was instigating the move toward re-affirming values of mammography; a few more "significant" trial updates, trials and meta-studies that produced more of statistical benefits from mammography screening, seemingly removed any doubt in its great life-saving effect.

Good part of the reason was that mammography screening had already become firmly entrenched as the centerpiece of the official policy's weaponry against breast cancer, and its benefits were generally accepted among medical professionals as advertised by its promoters.

Official backing, professional acceptance, career stakes, pride and big profits, all gave to the mammography "benefits" life of their own. Any contrary, unfavorable evidence was ignored, sidelined, or labeled as "flawed" or "incompetent".

For instance, the Canadian study, which showed no benefits from mammographic screening vc. clinical breast examination was, believe or not, investigated by a hired private investigation company  - and subsequently cleared - for tampering (Randomization in the Canadian National Breast Screening Study: a review for evidence of subversion, Bailar et al. 1997).

The study was given "stick and stone treatment" by the proponents of screening. Anything from unproven - and refuted, as mentioned above - accusation that the trial placed larger number of women with advanced cancers into its 40-49 year intervention group (Kopans; in fact, there was more clinically positive women in the control group), to alleging that the quality of its mammography was "indefensibly poor" (Kopans), while in fact it had documented above average efficacy for this age group, to numerous distortions and plain fallacies about the trial fed to media by the pro-screening side (for instance, that it had extraordinarily high rate of false negatives, or that it used ordinary X-ray units instead of mammography units).

The irony is that this Canadian randomized clinical trial actually raised quality level not only with respect to all other breast cancer studies from that time, but also with respect to most trials after it as well. Its deputy director illustrated all absurdity of the continuous dismissal of this study by X-ray mammography advocates as being of "low quality" and "flawed" (Baines, Rational and irrational issues in breast cancer screening, 2011).
 

Not a single one of these vital indicators of trial quality favors trial B; it is trial A that is superior in all these aspects. Yet it is trial B - the Two County Trial - that pro-mammography camp up to this day presents as a high quality and reliable, while dismissing trial A - the Canadian trial - as "low quality" and "flawed". The reason can be seen at the very bottom: the Two County trial is the only major trial after the very first (HIP) that produced statistically significant mortality reduction in the screened population.

On the other hand, the Canadian trial is the only one that came up

with near-zero overall life-saving benefit from screening.

It is this single aspect that placed these two trials at the center of controversy and determined which one will be honored and promoted, and which one denigrated and dismissed.

The above study design data are not complete, and that is more of a disadvantage for the Canadian trial, since the insight into many relevant aspects provided by, and its transparency, are unmatched, not only by the Two County trial, but also by any of the breast cancer trials before and after that.

Meanwhile, the publicity based on poorly designed, biased studies establishing "clear benefit" from mammography screening, was used to further promote the practice. The results from Two-County trial were, for instance, the deciding factor in the introduction of organized screening in Netherlands (1990), and among major factors prompting its introduction in the U.K.

While it took decades to unveil poor quality of the Two County trial, clear indications of flaws in the other major mammography-supporting trial, the New York trial, were noted and brushed aside at the time it came up with its results. Specifically, number of breast cancers diagnosed was nearly identical in the screened and control group - frankly, with those averaged in the screened group being actually larger, which is

logically incompatible with the study conclusion of
significantly lower mortality rate achieved by screening.

In fact, the main factor producing such outcome seems to be the exclusion of far more women with prior breast cancer from the treatment (screened) group,

directly lowering its mortality rate vs. that in the control group.

The only thing that changed in the practice of promoting mammography screening at any cost is that the main reason for doing so switched from the belief that it "has to be beneficial", to merely protecting interests of the screening establishment. The magnitude of facts distortion by die-hard supporters of standard mammography screening nowadays is well illustrated by this online article by a U.S. radiologist (The Journal of Lancaster General Hospital, PA). Here's the excerpt describing the Canadian trial (which consisted of two separate branches, for 40-49y and 50-59y age group):

"...Importantly, none of those large Canadian studies was a truly randomized controlled trial, since patients were assigned to the screening or no-screening groups only after a physical examination of the breasts. Since women with palpable masses were selectively assigned to the screening cohort, it contained 4X as many advanced cancers as the non-screened group. This difference inevitably altered the mortality statistics, which compromised the parameter by which the effectiveness of screening mammography was assessed. Errors in certification of the cause of death were also raised by the authors in the first study, a fact that was even noted by the authors of the paper. Compliance among the women in these studies was also a problem, with nearly 20% of those assigned to regular screening not getting these examinations over a 4-5 year period, and many women assigned to the no screening cohort getting screening mammograms outside the study. Questions have also been raised about the quality of mammographic examination, the skills of the interpreting physicians, design study, randomization, contamination of controls, follow-up, and ascertainment, thus further eroding the conclusions reached in this study..." (Controversies in screening mammography, N.K. Tanna, 2010)

Statements that neither branch of the Canadian trial was "truly randomized", and that its screening cohort "contained 4X as many advanced cancers" are plain false. As mentioned above, because of accusations by the mighty pro-screening camp, study's randomization was investigated more than a decade prior to this article, and no evidence of tampering was found.

As for "4X as many advanced cancers" in the screened group, it could be - unintentional? - mix up related to the fact that the screened group in the Canadian study had more node-positive cancers with four or more nodes involved detected. The actual numbers are 290 vs. 237 after five years, and 592 vs. 552 at 13-year follow-up for the screened population and controls, respectively. Nothing remotely close to "4X as many advanced cancers".

"Errors in certification" probably refers to the data presented in the trial paper where, due to confidentiality limitations imposed by hospitals, an external panel blind to the screening status could not investigate and confirm cause of death in all cases (for the 40-49 age group, it reviewed 67%  and 77% certificates for screened and control group, respectively, with the cause of death for the rest taken as reported on death certificate); this, of course, is not an "error", rather a cut above the Two County trial, in which reviewers weren't blinded to the status, and study authors were directly involved in determining the cause of death.

Compliance was actually better in the Canadian trial than in the Two County; "contamination" by women in the control group receiving occasional screening or diagnostic mammograms (about 20% averaged for both trial branches) is somewhat higher than the all-trial average (as published), but still within the range. Malmo study, for instance, had 25% contamination, and some studies (HIP, Stockholm, Edinburg) did not report it at all. The effect in the Canadian trial was estimated to be minor by the authors.

The unreferenced list of flaws at the end of the excerpt is a fairly good summary of other baseless objections to the quality of the Canadian study, serving as the pretext for its dismissal.

Also very typically, article author has

no single objection

to the design or execution of any of the trials that did produce more tangible - even in most cases still statistically insignificant - mortality reduction in the screened population. Swedish trials, collectively, are declared as "some of the best" (no specific reasons given), showing "nearly 30-45% decrease in mortality in the screened groups".

But wait, it gets even better: adding "recent updates, still unpublished", from author's conversation with Dr. Tabar (lead author of the Two County trial), "may show a nearly 65% reduction in mortality from breast cancer" due to screening X-ray mammography.

You may think that biased ramblings of an obscured U.S. radiologist don't matter much in the big picture, but think twice. It is such radiologists and the myths of screening mammography imposed as the official view that

many a woman depend on for information and guidance.

These ramblings are merely reflection of the official view supported by hard core advocates of the standard mammography screening practice, still dominant in the "official" medicine.

Conclusion

So, that was how it all started with the X-ray mammographic screening, and how it kept going: by assuming benefit, embracing all that seemingly supported it, while disregarding evidence to the contrary. The reality is that the X-ray screening mammography has become a major part of breast cancer public policy in some of the most developed countries, including U.S. It also became the backbone of quite a few academic careers, accepted practice for doctors, comforting, trusted  presence for millions of women, and a multi-billion dollar business.

But all this time it was standing on shaky ground.

In 1999, a small epidemiological study in Sweden - one of the most active countries in studying the effects of mammography screening - came up with a news outright shocking for most, although not entirely unexpected for a few. It found that in the ten-year period from 1986 to 1995, breast cancer mortality in over 600,000 Swedish women undergoing mammography screening declined only 0.8% vs. those that did not use the screening - much less than what the 11% officially accepted estimate was projecting (Sjönell and Ståhle, 1999).

This little study set in motion chain of events.