Miller et. al.’s study has further opened (perhaps blew the lid off?) the can of worms surrounding screening mammography and the pro-mammography contingent (mostly radiologists and cancer societies) are out with their ray guns blazing. They claim that it is nothing short of preposterous to question the validity of screening mammography (although that’s what science is, questioning). They say that the BMJ study involves 1980s technology (it does) and we can’t make 2014 guidelines based on equipment that is no longer in use (fair). They also counter that there are lots of good studies to support screening mammography (we’ll get to that in a bit).
Not to be flippant, but comparing other technology gives us an idea about how much mammography might have changed for the better. For example, in the 1980s cell phones (for the lucky few who could afford them) were so large they had to carried around in bags and you had to scream because they were just one generation removed from two tin cans and a string. Today, I deposited a check in my bank using my cell phone without leaving my house. The argument that 2014 technology might be able to do something more should be addressed.
So, I toddled on over to PubMed and typed in digital mammography mortality. This seemed the most logical search term as the question that we all really want answered is, “Will I live longer if I have regular screening mammograms?” I don’t want trials that tell me the size of a tumor that can be found digitally versus film. I don’t want an opinion piece. I want a clinical trial that tells me digital mammograms saves lives, because the BMJ study by Miller et. al. is a randomized clinical trial, so you need the same grade of medical evidence to bolster a counter argument. This is research rock-paper-scissors-dynamite, where a randomized controlled trial is dynamite and trumps everything else. You can only fight dynamite with dynamite.
There was ONE CLINICAL TRIAL. And it wasn’t even a general screening study, it was a screening high risk women study. I grabbed a screen shot I was so dumbfounded…
Maybe I did the search wrong (although what other search engine terms would you use if you wanted to know if digital mammography saves lives?).
I turned to the Cochrane Collaborative for help. People who truly know how to massage a search engine. A 2013 review found 8 clinical trials, but only 7 were of quality to be included. SEVEN. Let’s put this in perspective. We have massive screening programs in North America and there are only seven worthy studies for analysis? The way the American College of Radiology was frothing at the mouth I foolishly assumed there must be hundreds of randomized studies proving that digital mammography is super awesome at saving lives.
Here is a summary from the results section:
“Eight eligible trials were identified. We excluded a trial because the randomisation had failed to produce comparable groups.The eligible trials included 600,000 women in the analyses in the age range 39 to 74 years. Three trials with adequate randomisation did not show a statistically significant reduction in breast cancer mortality at 13 years (relative risk (RR) 0.90, 95% confidence interval (CI) 0.79 to 1.02); four trials with suboptimal randomisation showed a significant reduction in breast cancer mortality with an RR of 0.75 (95% CI 0.67 to 0.83). The RR for all seven trials combined was 0.81 (95% CI 0.74 to 0.87). We found that breast cancer mortality was an unreliable outcome that was biased in favour of screening, mainly because of differential misclassification of cause of death. The trials with adequate randomisation did not find an effect of screening on total cancer mortality, including breast cancer, after 10 years (RR 1.02, 95% CI 0.95 to 1.10) or on all-cause mortality after 13 years (RR 0.99, 95% CI 0.95 to 1.03).”
My conclusion? If the literature concerning digital mammography (the new, better mammography that wasn’t in the BMJ study) was so robust studies like the CNBSS would barely get the time of day in The Journal of Medical Obscurata. No one would care about a study on old equipment if studies on the newer equipment existed and truly showed a benefit. Honestly, it’s a little crude for the American College of Radiology and the American Cancer Society to bemoan a study for older technology when the proof that the newer technology is so great at saving lives seems rather, ahem, sparse.
Screening mammography makes money for radiologists and the companies that make the equipment. It drives a lot of Big Cancer’s fund raising and fuels a lot of the big pink Komen machine, but it doesn’t seem to me that anyone have proven with high quality randomized trials that modern, digital mammography actually saves lives.
We can’t take modern mammography on faith, we have to question until there is proof. That is science and the detractors of the BMJ study should take note.