Monday, 1 July 2013

Breast cancer screening fails to cut deaths

Twenty five years of breast cancer screening has failed to significantly reduce deaths from the disease, according to a landmark study.

Although the number of women who die from breast cancer is steadily decreasing, there is “no evidence” to suggest this is because of screening programmes first introduced in 1988, researchers from Oxford University said.

Daily Telegraph 11th June 2013

The significant decrease in deaths from breast cancer is among younger women who are not among those called in for regular screening. I would hazard a guess that this is because of the emphasis over the past few decades on self-examination.

It comes as no surprise to me that screening using mammography has not significantly reduced deaths from the disease and I can almost hear a certain Dr Martin Albright saying "I could have told you this in 1991."  I suppose having invested huge amounts of money in this programme, the NHS was obliged to run it for a number of years since the effectiveness may only have been measurable with time and a significant number of women being screened.

However, in 1991, during a lecture on "Screening" Martin outlined the criteria for an effective and safe screening programme and the ways in which mammography did not meet any of them. In 1991 folks! If I could find those lecture notes, the reasons outlined by Martin in 1991 why mammography did not meet any of the criteria for a safe, effective and reliable test would be shown, I think, to have been borne out in the intervening years of the programme.

How does mammography meet, or not meet, those criteria?

1) Is the test cost effective?

In 1991, Martin Albright said no and this seems to have been borne out in practice, since the average cost to the NHS is over £120 million a year and there has been no significant decrease in deaths from breast cancer.

2) Is it easy to administer?

The answer to this one has to be no, since it involves flattening the breast between two plates and passing a dose of radiation through the tissue. Flattening those mammaries is not an easy task.

3) Does it produce an acceptable number of false positives?

The chances of a false positive are increased with every mammogram a woman has.

False-positive screening mammograms are "very common," Dr. Brodersen toldMedscape Medical News. The cumulative risk in Europe and the United States of false positives in 10 screening rounds ranges from 20% to 60%. It is clear from this study that "psychosocial harms of the false results are substantial and last for years," Dr. Brodersen noted

A false positive result will lead to more tests, including biopsy and obvious stress and anxiety for the woman involved.

4) Does it produce an acceptable number of false negatives?

I think we can say no to this.

False-negative results. False-negative results occur when mammograms appear normal even though breast cancer is present. Overall, screening mammograms miss about 20 percent of breast cancers that are present at the time of screening...

...False-negative results can lead to delays in treatment and a false sense of security for affected women.

(Note: false negatives are more common in younger women because of the density of the breast tissue. As women age, there is less fatty tissue and therefore the breast tissue is less dense)

5) Are levels of discomfort reasonably acceptable to most women?

No! I don't think I need to say much about how incredibly painful, not just uncomfortable, it is when sensitive breast tissue is squashed to a thickness of  a few inches between two rigid plates.

6) Does the procedure, of itself, create problems?

Judging by the numbers of internet searches on the question of "Does trauma/injury to the breast cause breast cancer?" it would appear to be a commonly held belief/worry, but research on this question seems to conclude that there is little or no evidence to support the theory.

One study suggests a link: Cancer Research UK

No evidence:

Q: Can an injury to my breast develop into breast cancer?

A: Injury to the breast does not cause breast cancer. In some cases, the breast may become bruised after an injury and, in rare cases, develop a non-cancerous lump called fat necrosis. Fat necrosis is not dangerous, and the symptoms usually subside within a month. If you have a lump in your breast and are concerned that it may be breast cancer, consult with your doctor immediately.

What about the radiation, then? Safe levels?

Mammography was introduced in the USA in the 1970s and at that time radiation levels were significantly higher than when the procedure was introduced in the UK. However...

Despite better technology and decreased doses of radiation, scientists still claim mammography is a substantial risk. Dr. John W. Gofman, an authority on the health effects of ionizing radiation, estimates that 75 percent of breast cancer could be prevented by avoiding or minimizing exposure to the ionizing radiation. This includes mammography, x-rays and other medical and dental sources.

From the same source:

Cancer research has also found a gene, called oncogene AC, that is extremely sensitive to even small doses of radiation. A significant percentage of women in the United States have this gene, which could increase their risk of mammography-induced cancer. They estimate that 10,000 A-T carriers will die of breast cancer this year due to mammography. (2005)

Compression of breast tissue can cause cancerous cells to travel to distant sites.

Cancer Risks from Breast Compression

As early as 1928, physicians were warned to handle "cancerous breasts with care— for fear of accidentally disseminating cells" and spreading cancer (7). Nevertheless, mammography entails tight and often painful compression of the breast, particularly in premenopausal women. This may lead to distant and lethal spread of malignant cells by rupturing small blood vessels in or around small, as yet undetected breast cancers.

From the source cited above:

Radiation Risks

Radiation from routine mammography poses significant cumulative risks of initiating and promoting breast cancer.

So, does the process of mammography cause problems of itself?

It would appear that the answer to this is yes. Cumulative doses of radiation are thought to be a risk factor for the development of cancer of the breast, particularly in women who carry a particular genetic anomaly, who are therefore more at risk. 

And for me, it seems to be a no-brainer that compression to the breasts can cause cells to break off and travel to distant sites, presenting a high risk of the development of metastases. (secondary tumours) 

For me, the development and continued use of mammography as a screening test for breast cancer is left brain thinking. Mostly we are told that the left brain is logical, rational, literal and the right brain is creative and imaginative.   Robert Ornstein suggests text/context. When I view and object, my left brain tells me descriptive things about it: this thing I'm looking at is living, it's hairy, it's brown. My right brain places this thing in the context of similar things I have encountered and tells me "It's a dog!" Similarly, my left brain says there are things in the water and they're moving and my right brain, comparing them to similar things I've seen before, to place them in a context, says "They're gill-bearing aquatic craniates." (Do I go into the chippie and ask for gill-bearing aquatic craniate and chips? Of course I don't! I'm vegetarian!) 

So, the left-brainer develops machines. And oh what magnificant machines they are! These machines can flatten breasts and when we pass a nice dose of radiation through, we can possibly detect cancer. That's the straight line thinking of the left brain. When right brain and left brain work in harmony, some context is added here - uh, hang on a wee minute, Jimmy, I've seen this kind of thing before: radiation can cause cancer and what kind of head banger can't work out that if you squash breasts as flat as possible, significant harm could result? 

So, on the six criteria for a safe and effective screening test, mammography scores a big FAIL! 

There is also, to be added here, the problem of over-diagnosis. Some breast cancers are so slow-growing that they will never become symptomatic within the natural life expectancy of the individual, but these tumours may be picked up by mammography and unnecessary treatment started, which of course can be traumatic and lead to further treatment being necessary. 

The most informative analysis in Zackrisson et al's study is the comparison of the cumulative incidence of breast cancer in the screened and the non-screened groups of women born between 1908 and 1922 and randomised between 1976 and 1978.1 This is a mature cohort with follow-up to 2001 when about 60% of the women had died. The main finding is a 10% increase in the lifetime occurrence of breast cancer (including cancer in situ) in the screened group.

In a population where the lifetime risk of breast cancer is 8% and the lifetime risk of dying from breast cancer from age 50 onwards is 2.5%, screening 250 women may prevent about one death from breast cancer. Screening would, however, also lead to the over-diagnosis of two cases. The woman whose death from breast cancer is prevented receives all the important benefit, whereas the two over-diagnosed women pay part of the price by becoming breast cancer patients and undergoing treatment. We cannot predict, however, which three women these will be. (23/03/206)

For every woman whose life is saved, two women will be over-diagnosed, gaining the status of breast cancer patients and undergoing treatment? I don't think I like the odds on that, however slim they may be, of being one of those two. 

And finally, if mammography is so unsafe and unreliable, why is so much effort being put into bringing more women onto the programme? And if the significant decrease in deaths from breast cancer is among those women too young for regular screening, why was the "expert" on Radio 4's Today programme suggesting that the programme be extended to include those women? They're doing alright without it! Seems like a no-brainer to me! 

There are potentially safer screening tests being tried out. More on those another time! 

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