Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

The whole point of cancer screening is to “detect life-threatening disease at an earlier, more curable stage.” So, an “[e]ffective cancer-screening program…[would] therefore…increase the incidence of cancer detected at an early stage [because you’d find all these tiny cancers you would have missed before] and [therefore] decrease the incidence of cancer presenting at a late stage”—because you would have cut out all the little cancers you found, pulling them out of circulation.

But, that’s not what appeared to happen with mammograms. As mammography ramped up in the 80s, the first part happened: the diagnosis of early cancers shot up. And so, what we’d like to see is like a mirror image of this, going the other way, for late-stage cancers. If you caught it early, it wouldn’t be around for late. But, that didn’t happen. Late-stage cancer incidence didn’t seem to drop much at all.

Another way to look at this is to compare mammogram rates around the country. The more mammograms you do, the more heavily screened the population is, the more early cancers you pick up. Great. And late, advanced disease should go down too, right? But, it doesn’t. We’re taking all these early cancers out of circulation—surgery, radiation; and so, there should be about the same number fewer late-stage cancers found. But, that didn’t happen. Mammograms catch a lot of small cancers, but with no concomitant decline in the detection of larger cancers. That would explain this. The more mammograms you do, the more cancer you find. But, death from breast cancer doesn’t seem to change much.

Wait a second; you just cut out tens of thousands of cancers; why aren’t there that many fewer women dying? “Together, these findings suggest widespread overdiagnosis”—meaning cancer picked up on mammograms that would have never progressed to the point of presenting during the woman’s lifetime, and so, wouldn’t even have been noticed, or caused “any harm” had it never been picked up at all.

So, if removing all these early ones didn’t lead to that many fewer late ones, that suggests that most would have never progressed during that time, or even go away on their own. That “could explain almost all [that] increase in incidence.” And indeed, “many invasive breast cancers detected by repeated mammography screening do not persist to be detected later, suggesting that the natural course of many of the [mammogram]-detected invasive breast cancers is to spontaneously regress [spontaneously disappear].”

We’ve known for more than a century that even serious metastatic breast cancer can sometimes just spontaneously go away. The problem is that you can’t tell which is which. So, if you find it, the natural inclination is to treat it, which can be especially tricky for ductal carcinoma in situ: DCIS, so called stage zero breast cancer. This is what it looks like. “Ductal” means in the breast ducts, “carcinoma” means cancer, and “in situ” means in place, in position, not spreading outside of the duct. And, it can create these tiny calcifications that can be picked up on mammogram.

The whole point of mammograms was “to identify early invasive disease.” So, the large numbers of DCIS they found “were unexpected and unwelcome.” “Prior to the advent of [mammogram] screening,…DCIS…made up approximately 3% of breast cancers detected,” but now accounts for a significant chunk. The cells “look like invasive cancer…,and therefore the presumption was made that these lesions were the precursors of cancer” [stage zero cancer] and that early removal and treatment would reduce cancer incidence and mortality.”

“However, long-term [population] studies have demonstrated that the [surgical] removal of 50 000 to 60 000 DCIS lesions annually has not been accompanied by a reduction in the incidence of invasive breast cancers. This is in contrast to [our] experience with remov[ing]…colon…polyps” with colonoscopy or precancerous cervical lesions thanks to Pap smears, “in which the removal of precursor lesions has led to a decrease in the incidence of colon and cervical cancer….” Those are cancer screening programs that work.

Radiologists argue that “overdiagnosis” isn’t so much the problem as “overtreatment.” Yeah, it sucks to get a breast cancer diagnosis, even though it would never have hurt you. But, you don’t know that at the time. So, most women undergo aggressive surgical and radiation treatment. Yeah, but if you compare the 10-year breast cancer survival for women with low grade DCIS, among those who chose not to go to surgery at all? 1.2% of them died of breast cancer within a decade. But, in that same decade, those that went to surgery instead for a lumpectomy or a full mastectomy to cut it out—1.4% died from breast cancer. So, surgery appeared to make no difference.

That’s why there are currently randomized, controlled trials to put it to the test. But, it’s “incredibly difficult to convince a patient with…DCIS not to” just want to get it cut out. “The fear of cancer paralyzes patients,” who may resort to “drastic [excessive] measures,” like getting a double mastectomy. How can we prevent that? How about we change its name? A National Cancer Institute panel has recommended dropping the “carcinoma” part. Let’s just call it an “indolent lesion of epithelial origin”—”use language that engenders less fear.” How bad can an “IDLE” tumor be?

Another option to avoid this dilemma is just not get screened in the first place, but women aren’t typically told about any of this. Less than one in 10 women were aware that mammograms carried any potential harms at all, and more than nine out of 10 were unaware that some breast cancers never cause problems. Few were told about DCIS, but when informed about it, most wished they were told before they signed up.

Once a cancer is detected, it is currently not possible to distinguish life-threatening from potentially harmless cases. “Therefore, overdiagnosis can only be avoided by abstaining from [routine mammograms] altogether.”

That’s how this researcher explained her own decision away from screening. “[W]orried by the possibility that [she] could be seriously harmed by the treatment of a cancer that would never have affected [her] health,” and given that the only way to avoid opening that Pandora’s box was by not getting mammograms, she decided to try improving her diet and lifestyle to prevent getting breast cancer in the first place.

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