« The sanctity of diaries | Main | A few addendums to previous blogs »

Screening mammography

The last two weeks have seen a flurry of comments about the merits of screening mammography for women under the age of 50. There is nothing new here. This debate has been going on for more than 20 years now. Evidence has existed for years, that in population terms, screening younger women does not save lives from breast cancer and probably harms more woman than it helps. The US has chosen for years to ignore this, while the rest of the western world generally does not promote screening to women under 50.

Before we get into the details let me make two things perfectly clear:

  • Screening versus diagnostic mammograms: the general public often doesn't understand the difference between screening and diagnostic mammograms. Screening takes a healthy population of women with absolutely no symptoms and tests them with regular mammograms. A diagnostic mammogram, on the other hand, is done when there is a detectable lump, a discharge,  a change or puckering in the skin or when a woman is found or suspected by family history to carry BRCA-1 or BRCA-2 genes. The debate about mammograms is around screening healthy women with no symptoms or genetic risk and its value in saving lives. If you or a loved one at any time has any symptoms  or carry the gene for breast cancer, get a diagnostic mammogram as fast as you can. In the same way, screening breast self exams -- which means teaching healthy symptomless women how to check their breasts in a routine way at the same time ever month -- has not been found to help. That is completely different from the need for all women to simply know her breasts and notice any change -- a lump, a puckering, a discharge or thickening of the skin. As soon as you have a symptom, get into the doctor right away.
  • The need for clear informed consent and personal decision-making:  A woman  must be the master of her own body. If, with her family doctor, a woman at any age is fully aware of the pros and cons of mammograms and decides she needs one or wants one, and the doctor agrees, she should be able to get one. But as I will detail below, there has been a lack of clear informed consent around mammograms. Only the benefits, and none of the downsides, are widely promoted in the invitations to screening programs. But, if a woman knows the pros and cons and decides to get one, I absolutely support that right. I personally know many women who chose screening and had early cancers, mostly DCIS,  found. They firmly believe this saved their lives and I support their right to believe that and make that choice. More informed consent is needed.

Now that those two things are clear, let me tell you a story. Back in 1987, when I was medical reporter at the Vancouver Sun, I got a call from the BC Cancer Agency that the Canadian National Breast Cancer Screening Study was comparing the outcomes of women screened to women not screened in huge numbers -- more than 90,000 Canadian women. But there was a problem - not enough women knew about the study and so not enough were signing up to take part. I wrote a story about a woman whose breast cancer was found on a screening mammogram, and how grateful she was. And I urged women to take part in this important study. The Cancer Agency had so many calls in the week after my story ran -- more than 3,000 -- that they had to put in extra phone lines. The BC arm made its target number for the study in part based on my promotion of it. I firmly believed early detection was the way to go.

But then, around 1988/89, I began to hear concerning rumors among my sources that results of the study were astonishing and confounding. In the 40 to 49 age group, more women were dying in the screened group than were dying in the control group. This did not make sense. We all believed so firmly that early detection would save lives, and that the earlier that screening was started, and a cancer detected, the better. No one wanted to believe that finding it earlier might in fact be harmful.  Canadian lead researcher Dr. Cornelia Baines says the data about worse outcomes in screening in younger women started showing as early as 1983, but by the early 1990s, with more than 90,000 women studied,  it was clear - the young mammography group had more deaths, more false positives and more overdiagnosis ( treatment of harmless cancers) than the control group. When Baines et al published the results in 1992 they were roundly criticized, their study methods were faulted (there was nothing wrong with the study) and the Canadian team's credibility was assaulted. It was shocking to see how ideology trumped the research. The message was ignored and the messengers shot instead.

But two otherr large European controlled studies found exactly the same result -- women under 50 had more deaths.  UK surgeon and breast cancer expert Dr. Michael Baum, who in in the 1980s was the strongest proponent in that country for mammography and set up its national screening program, has become one of its strongest and most vocal critics. Baum is particularly concerned by the huge increase in ductal carcinoma in situ ( DCIS) found in women under 50 who have mammograms.

Here is what Dr. Baum has said widely in various interviews, including to me in an article I did on DCIS in spring 2008 Best Health, about his theory about what is occurring:

" Ductal carcinoma in situ is probably not a good word, and we should call it latent cancer. These latent cancers, particularly in premenopausal women, are grossly over-represented in women given mammograms--something like five times more, compared to what you would expect. This suggests that if left to their own devices, these latent cancers might never trouble a woman. But if you identify these latent cancers and biopsy them, you have traumatized the area. You immediately trigger the natural healing mechanisms, and natural healing mechanisms involve angiogenesis ( formation of new blood vessels.) So, effectively, the biopsy could be considered an angiogenic switch. You take a latent cancer that would never hurt a woman, biopsy it, turn on the angiogenic switch, and it ceases to be latent. A latent disease becomes an aggressive disease."

This theory of angiogenesis is highly controversial and you won't hear it discussed much, but it is strongly supported Michael Retsky, PhD, a researcher at Harvard Medial School and the late, famed researcher Judah Folkman, also of Harvard, who is credited as the father of angiogenesis research in many disease processes including cancer. Another interesting finding that might support the theory that mammography may somehow help turn on a switch making some breast cancers more aggressive. For years researchers have known about "interval cancers"  -- breast cancer that shows up, suddenly between the screening as a felt lump in women who have been having mammograms every year or two.  There is no evidence of a cancer at all on the screen, but then one suddenly grows rapidly before the next scheduled mammogram. Interval cancers are usally more aggressive than those found at the time of screening or those found in women who have never undergone screening. They don't know why interval cancers are particularly nasty, but Baum theorizes that perhaps radiation or the intense squeezing of the breast during the screen may switch on the healing response of angiogenisis that also spurs a cancer growth.

Baum resigned from the UK screening program in the 1990s when it refused to share the pros and cons with all women taking part in screening as a necessary discussion about informed consent. He believes that fully informed women over the age of 50 should choose for themselves as there is evidence past age 50 it saves lives, but he is on the record saying: "To promote screening mammography to women under the age of 50 is absolutely unethical."

But let's take a closer look at that age of 50 -- that age is chosen because the median age of menopause in western women is around 49.  Onset of menopause ranges from the early 40s to the late 50s. Some women do not experience menopause ( a full year without a menstrual period) until age 58 or 59. The evidence is that it is likely menopause not age, that is the defining factor of whether screening mammograms are helpful.  ( It could again be angiogenesis and the menstrual cycle, some theorize.) The evidence is convincing enough for me that I have decided I will not undergo a screening mammogram until I have had one full year of cessation of menstruation. The best results for screening is among women aged 60 to 69, likely because all women by that age are menopausal.

Here is another fact that more women should know. The huge drop in the use of hormone replacement therapy corresponds exactly, with a lag time, with a significant drop in breast cancer incidence. In fact, more lives may be saved by not doing HRT than from screening.  There was a 13 per cent drop in hormone receptor positive breast cancer between 2001 and 2004 and an 8 per cent drop in a single year ( 2002/2003) that tracks exactly to the sudden stop of HRT by millions of women following the 2001 results of the Women's Health Initiative, that found HRT was harming women.

Look at these two graphs from the New England Journal of Medicine and note the  drop  corresponds to the sudden decline in prescriptions for HRT. Although the issue is still being debated, a similar decline was seen in Canada, Spain and the UK, and a special study by regions in California also showed the same result. Click to enlarge the thumbnail to better read the graph, from New England Journal, Berry et al, April 19, 2007 

For those of you wanting more references, here are a few ones to start. The literature is huge. Just google pubmed and go to the National Library of Medicine data base. You could be reading for hours. I am citing the British Medical Journal and European journals primarily because there seems to be a more open discussion of the pros and cons over the last decade in Europe than in North America,  which may be interesting to Canadian women. Here in North America we still shoot the messenger, as has been seen by the coverage of the past week. Thus, I am wearing my flak jacket.

H Gilbert Welch. Overdiagnosis and mammography screening.
BMJ 2009 339: b1425. [Extract] [Full Text]

Zackrisson S, Andersson I, Janzon L, Manjer J, Garne JP. Rate of over-diagnosis of breast cancer 15 years after end of Malmö mammographic screening trial: follow-up study. BMJ 2006;332: 689-91.[Abstract/Free Full Text]

Duffy SW. Some current issues in breast cancer screening. J Med Screen 2005;12: 128-33.[Medline]

Moller B, Weedon-Fekjaer H, Hakulinen T, Tryggvadottir L, Storm HH, Talback M, et al. The influence of mammographic screening on national trends in breast cancer incidence. Eur J Cancer Prev 2005;14: 117-28.[CrossRef][ISI][Medline]

H Gilbert Welch, Lisa M Schwartz, and Steven Woloshin. Ramifications of screening for breast cancer: 1 in 4 cancers detected by mammography are pseudocancers
BMJ 2006 332: 727. [Extract] [Full Text]

 Michael Baum. Ramifications of screening for breast cancer: Consent for screening BMJ 2006 332: 728. [Extract] [Full Text]





Posted on Thursday, November 26, 2009 at 04:22PM by Registered CommenterAnne | Comments1 Comment

Reader Comments (1)

Thanks for this article, Anne. I've been feeling guilty for years about my procrastination in making the appointment for a screening mammogram. Now I'm feeling relieved, and wondering why, as a person who follows at least mainstream health coverage, I have been unaware of this disturbing information.
November 27, 2009 | Unregistered CommenterDebbie Wilson

PostPost a New Comment

Enter your information below to add a new comment.

My response is on my own website »
Author Email (optional):
Author URL (optional):
All HTML will be escaped. Hyperlinks will be created for URLs automatically.