bunch of crap! I don't even know where to begin! When I calm down, I need to write a complete and total dismissal of this so-called study. Did I mention what a load of crap this study is?

*susan*

I wonder if they compared TYPES of cancer.  If all of them had ILC, then yes, a good portion of mammograms would miss it, so whether you do self exams or the mammo, it's a luck of the draw on if it is found at all.  IDC, different story for most women.

Argh!  The chart I tried to paste in came out as gobbledegook...  I'll try to rectify the problem because the chart showed that our yearly exposure to naturally-occuring radiation (from our bodies, the soil, our food, our drinking water, etc.) was quite significantly higher than yearly exposure to medical radiation....

Which, then, begs the question if the additional radiation from medical sources is enough to "tip-the-balance", so to speak or if it is negligible in the wider scheme of things.

Another thing I'd like to find information on is how long does it take for certain radiation exposures to dissipate over time.  Or do they?  For example, how is cumulative effect impacted if, for example, someone like me who had radiation treatment for breast cancer, never had any more exposure to medical radiation for the rest of my life.  Does my cumulative effect remain constant?  Or is there a relative component?

Exactly.  So far, that is information that I have been unable to pin down...

We all come with a very personal anecdotal opinion/relationship to mammography and its use in detecting cancer, and it is very difficult to look at the bigger picture, particularly if our cancer was found by a mammogram and we feel our lives were saved by early detection. However, as AlaskaAngel states, this is a major study and cannot be dismissed purely from our personal perspective. For example, in the UK women over 50 are recommended to have mammograms every three years, yet this does not lead to more deaths from breast cancer. Early detection does not necessarily lead to reduced mortality and has been shown to lead to over-treatment.

ziggypop, there are many arguments that DCIS is a perfect example of over-treatment, but the sad thing is that no one can define when.  Men over a certain age with prostate cancer are told the same thing...something else will get them if they have a slow grower and that most DCIS will not become invasive.  The problem is WHICH ones.  Since no one can tell the men or women which are the aggressive pre-cursors, we treat them all as aggressive.

Wallycat - I understand the idea about DCIS and that it potentially will never become invasive - but to my mind I would certainly rather overtreat with procedures that don't kill people than undertreat and have people die as a result. If you take 100 people with DCIS and treat all of them, you may only be saving 10 lives (certainly you are saving that many because at least ten it seems have a micro invasion or when they're pathology results from surgery come back they have some small amount of IDC), so 90 are being overtreated - to my mind that still beats 10 dying. 

And the fact that the leave this group out of the study just seems absurd - at a minimum you would with a study keep track of the cases of DCIS that are found with mammography - I read the study and I can even figure out what they did with these people. How did they count them - I mean if they had a control group that they weren't going to find DCIS in (because they didn't get mammograms) then it seems that they would have at least kept track of whether there were more cases of IDC found LATER in that group. It's not just the RATE of survival that counts - it's also the amount of cases you prevent from actually being counted as BC in the first place.

Here's the actual report BMJ article about the study:

Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial

I obviously need to read it again when I'm able to think more clearly, because after a first reading, I'm totally confused.  Although mortality rates are equal between the mammogram and non-mammogram groups, survival rates are very different.  Huh??

The 25 year survival was 77.1% for women with tumours of less than 2 cm,
compared with 54.7% for tumours greater than 2 cm (hazard ratio 0.46,
95% confidence interval 0.37 to 0.58; P<0.001). The 25 year survival
was 70.6% for women with breast cancer detected in the mammography arm
and 62.8% for women with cancers diagnosed in the control arm (0.79,
0.64 to 0.97; P=0.02). The 25 year survival for women with a palpable
cancer was similar between women in the mammography arm and control arm
(66.3% and 62.8%). The 25 year survival of women with breast cancer
diagnosed by mammography only (non-palpable) was 79.6%. In the
mammography arm, the survival of women with a non-palpable cancer was
much longer than that of women with a palpable cancer (0.58, 0.41 to
0.82; P<10⁻⁴) as was the survival of women with a screen detected cancer compared with interval cancer (0.61, 0.45 to 0.82; P=0.001).

This survival difference is explained away here:

In this analysis of findings from the Canadian National Breast Screening
Study, we have extended the previously reported follow-up at 11-16
years to 25 years, and for the first time report an estimate of the amount of over-diagnosis resulting from mammography screening.  We still found no reduction in breast cancer mortality from mammography
screening in a programme offering five annual screens, neither in women
aged 40-49 at study entry nor in women aged 50-59. Although the
difference in survival after a diagnosis of breast cancer was
significant between those cancers diagnosed by mammography alone and
those diagnosed by physical examination screening, this is due to lead
time, length time bias, and over-diagnosis.

I'm also unclear on how they've defined "over-diagnosis".  

At the end of the screening period, an excess of 142 breast cancers
occurred in the mammography arm compared with the control arm, and at 15
years the excess remained at 106 cancers. This implies that 22%
(106/484) of the screen detected invasive cancers in the mammography arm
were over-diagnosed. This represents one over-diagnosed breast cancer
for every 424 women who received mammography screening in the trial.
Assuming that nearly all over-diagnosed cancers in the Canadian National
Breast Screening Study were non-palpable, 50% (106/212) of mammogram
detected, non-palpable cancers were over-diagnosed.

What determines that a cancer was "over-diagnosed" versus being found early, treated and the patient survived? Is it just because the mammography group was found to have more cancers, therefore it's assumed that all these extra cancers were over-diagnosed?  

I'm lost. 

Having followed the mammography controversy for several years, all I can say is that if the vocal radiologists continue to believe that their evidence is "better" than what so many studies are telling us is to the contrary, then we will NEVER get the type of breast cancer screening' what ever that is, that we truly deserve and need.  Diagnostic mammograms save lives and population based screening mammograms also save lives, but not as many as we are led to believe.  H. Gilbert Welch's book, Over diagnosed, lays out the ccontroversy brilliantly, as does the late radiologist, Handel Reynolds in his book, The Big Squeeze.

Hi all

As I posted on another thread- the physician community is discussing this as well.  Had a great chat with a general surgeon just yesterday and he believes that there is not necessarily over-diagnosis but there is over-treatment and will continue to be because unless you can know what cancers can progress from in-situ to invasive docs are going to treat them all. He also noted in his personal practice that he frequently sees women with high grade cancers that when he looks back over the mammography history, even the suspicion or as he called it "maybe a shadow you see with one eye closed is not always easily readily seen.  I asked if these were young women primarily? Answer no and many with inflammatory breast disease as well. 

I do disagree with the rationale that its somehow okay to overtreat with things that won't kill you as one poster stated.  That would be exactly the thinking for all those antibiotics prescribed for a mild infection or even a virus and resulted in drug-resistant organisms we battle today. It is also why the US spends a much higher percentage of its GDP on healthcare than other countries do. Do I disagree with this not at all!!

I personally think this is round 2 being presented in the media from previous publicized  recommendations backing off on annual screening mammography. I did not have breast cancer when that was all playing out but I remember the concern and public outcry when less frequent screening was mentioned- now low and behold this study says there is little value over time.  hmmmm could there be any correlation between healthcare reform and this focus on mammography and its benefits (or not).  just my 2 cents

Hi all -- see what BCO has to say about this study:

Canadian Study Questions Value Of Mammograms for Women Aged 40 to 59; Experts Say Research Is Flawed

Moderators....who at bco is writing the position attached to your link regarding the Canadian study.  Was it written by a radiologist?  I think there should be a name and their affiliations attached so readers can make a more informed opinion.

Bad....no one can make an argument that any particular person's life was saved due to a population based screening mammogram and there in lies the quandary....Until there is an acknowledgement from radiologists and advocacy groups and politicians that screening mammograms may not save as many lives as previously believed, then cancer will be the winner. Once there is an acknowledgement, then we can begin the discussion of how to finance better screening tools that will ABSOLUTELY make a difference at saving lives.....

For the record, both my cousin and I were diagnosed with breast cancers that screening mammograms missed....