Everybody knows that colonoscopy is the best test to screen for colorectal cancer and that colonoscopies save lives. Everybody may be wrong. Colonoscopy is increasingly viewed as the gold standard for colorectal cancer screening, but its reputation is not based on solid evidence. In reality, it is not yet known for certain whether colonoscopy can help reduce the number of deaths from colorectal cancer. Screening with fecal occult blood testing (FOBT) and flexible sigmoidoscopy are supported by better evidence, but questions remain. It seems our zeal for screening tests has outstripped the evidence.
Statistics show that the life-time risk for an adult American to develop colorectal cancer (CRC) is approximately 6%. Colorectal cancer is the second leading cause of cancer deaths in the United States. In the US there are currently 146,970 new cases and 50,630 deaths each year. Between 1973 and 1995, mortality from CRC declined by 20.5%, and incidence declined by 7.4% in the United States.
The US Preventive Services Task Force (USPSTF) recommends screening for colorectal cancer (CRC) using fecal occult blood testing, sigmoidoscopy, or colonoscopy, in adults, beginning at age 50 years and continuing until age 75 years. (more…)
Editor’s note: Given the controversial nature of the topic, I think it’s a good time to point out my disclaimer before this post. Not that it’ll prevent any heated arguments or anything…
The Science-Based Medicine blog was started slightly over two years ago, and this is a post I’ve wanted to do since the very beginning. However, since January 2008, each and every time I approached this topic I chickened out. After all, the topic of abortion is such a hot button issue that I seriously questioned whether the grief it would be likely to cause is worth it. (Take the heat generated any time circumcision is discussed here and ramp it up by a factor of 10.) On the other hand, there is so much misinformation out there claiming a link between abortion and the subsequent development of breast cancer when the data simply don’t support such a link, and the name of this blog is Science-Based Medicine. Why should I continue to shy away from a topic just because it’s so religiously charged? More importantly, in my discussion how can I focus attention on the science rather than letting the discussion degenerate into the typical flamefest that any discussion of abortion on the Internet (or anywhere else, for that matter) will almost inevitably degenerate into. Indeed, such discussions have a depressing near-inevitability of validating Godwin’s law not once but many times — usually within mere hours, if not minutes.
My strategy to try to keep the discussion focused on the science will be to stay silent about my own personal opinions regarding abortion and, other than using it to introduce my trepidation about discussing the topic, the religious and moral arguments that fuel the controversy. That’s because the question of whether abortion is the murder of a human being, merely the removal of a lump of tissue, or somewhere in between is a moral issue that, at least as far as I’m concerned, can’t ever be definitively answered by science. That is why it is not my purpose to sway readers towards any specific opinion regarding the morality of abortion. Indeed, I highly doubt that any of our readers care much about my opinions on the matter. On the other hand, I would hope that I’ve built up enough trust over the last two years that our readers will be interested in my analysis of the existing data regarding something another related issue. It is my purpose to try to dispel a myth that is not supported by science, specifically the claim that elective abortion is causes breast cancer or is a very strong risk factor for its subsequent development. That is a claim that can be answered by science and, for the most part, has been answered by science with a fairly high degree of certainty. Despite the science against it, the medical myth that abortion causes breast cancer or vastly increases the risk of it is, like the myth that vaccines cause autism, a manufactroversy that won’t die, mainly because it is largely fueled by religious beliefs that are every bit as immune to science as the ideological beliefs that drive the antivaccine movement.
Science-based medicine consists of a balancing of risks and benefits for various interventions. This is sometimes a difficult topic for the lay public to understand, and sometimes physicians even forget it. My anecdotal experience suggests that probably surgeons are usually more aware of this basic fact because our interventions generally involve taking sharp objects to people’s bodies and using steel to remove or rearrange parts of people’s anatomy for (hopefully) therapeutic effect. Ditto oncologists, who prescribe highly toxic substances to treat cancer, the idea being that these substances are more toxic to the cancer than they are to the patient. Often they are only marginally more toxic to the cancer than to the patient. However, if there’s one area where even physicians tend to forget that there is potential risk involved, it’s the area of diagnostic tests, in particular radiological diagnostic tests, such as X-rays, fluoroscopy, computed tomography (CT) scans, and the variety of ever more powerful diagnostic studies that have proliferated over since CT scans first entered medical practice in the 1970s. Since then, the crude images that the first CT scans produced have evolved, thanks to technology and ever greater computing power, to breathtaking three dimensional-views of the internal organs. Indeed, just since I finished medical school back in the late 1980s, I’m continually amazed at what these new imaging modalities can accomplish.
The downside of these imaging modalities is that most of them require the use of X-rays to produce their images. True, over the last 15 years or so MRI, which uses very strong magnetic fields and radiofrequency radiation rather than ionizing radiation to produce its images, has become increasingly prevalent. MRI is great because it produces more contrast between different kinds of soft tissue than CT scans do. However, CT tends to be superior for examining calcified organs, such as bone. (The breast surgeon in me notes that breast MRI is pretty much useless for detecting microcalcifications, an important possible indicator for cancer.) Also, MRI scans require a prolonged period of laying still in a very tight tube, which is a problem for patients with any degree of claustrophobia, although “open” MRIs are becoming increasingly available. More importantly for the quality of images, because they require a patient to lie more still than a CT, MRIs tend to be prone to more motion artifacts, which is perhaps why CT is more frequently used to image the abdomen other than large solid organs such as the liver. The point is that, although MRI is becoming more prevalent, CT scans aren’t going away any time soon. They have different strengths and weaknesses as imaging modalities and are therefore best suited for different, albeit overlapping, sets of indications.
A while back I wrote about rethinking how we screen for breast cancer using mammography. Basically, the USPSTF, an independent panel of physicians and health experts that makes nonbinding recommendations for the government on various health issues, reevaluated the evidence for routine screening mammography and concluded that for women at normal risk for breast cancer, mammography before age 50 should not be recommended routinely and should be ordered on an individualized basis, and that routine formalized breast self-examination (BSE) should also not be routinely recommended. In addition, for women over 50, it was recommended that they undergo mammography every other year, rather than every year. These recommendations were based on a review of the literature, including newer studies.
To say that these new recommendations caused a firestorm in the breast cancer world is an understatement. The USPSTF was accused of misogyny; opponents of health care reform leapt on them as evidence that President Obama really is preparing “death panels”; and HHS secretary Kathleen Sebelius couldn’t run away from the guidelines fast enough. Meanwhile, a society I belong to (the American Society of Breast Surgeons) issued a press release accusing the USPSTF of sending us back to the “pre-mammography” days when, presumably women only found breast cancer after it had grown to huge size (just like Europe and Canada, I guess, given that the recommendations for screening there closely mirrors those recommended by the USPSTF). Meanwhile, in the most blatant example of protecting its turf I’ve seen in a very long time, the American College of Radiology went full mental jacket with a press release that was as biased as it was insulting. Meanwhile some physicians even likened the recommendations to going back to being like Africa, Southeast Asia and China as far as breast screening goes in that he actually speculated that he’d now become very busy treating advanced, neglected breast cancers. Unfortunately, as Val pointed out, the communication of the USPSTF guidelines to the public was almost a perfect case study in how not to do it. Even though the science was in general sound and the USPSTF recommendations were in essence close to identical to what other industrialized nations do, they were communicated in just such a way as to produce maximum misunderstanding and misuse for political purposes.
Despite all the hysterical and in some cases disingenuous attacks on the new guidelines, there is one criticism that actually resonates with me because I work at a cancer center in a very urban environment with a large population of African-American women. Last week I heard on NPR this story:
It’s been about a year and a half since I’ve written about this topic; so I thought I’d better update the disclaimer that I wrote at the beginning:
Before I start into the meat of this post, I feel the need to emphasize, as strongly as I can, four things:
- I do not receive any funding from the telecommunications industry in general, or wireless phone companies in particular. None at all. In other words, I’m not in the pocket of “big mobile” any more than I am in the pocket of big pharma.
- I don’t own any stock in telecommunications companies, other than as parts of mutual funds in which my retirement funds are invested that purchase shares in many, many different companies, some of which may or may not be telecommunications companies.
- None of my friends or family work for cell phone companies.
- I don’t have a dog in this hunt. I really don’t.
There. That’s better. Hopefully that will, as it did last time, serve as a shield against the “shill” argument, which is among the frequent accusations I hear whenever I venture into this particular topic area. So, as I did back in 2008, I just thought I’d clear that up right away in order (hopefully) to preempt any similar comments after this post. Unfortunately, as I have known for a long time, I’m sure someone will probably show his or her lack of reading comprehension and post one of those very criticisms of me. It’s almost inevitable, either here or elsewhere. Posting such disclaimers never seems to work against the “pharma shill” gambit when I write about vaccines or dubious cancer cures. Even so, even after nearly ten years involved in skepticism and promoting science-based medicine, hope still springs eternal.
There are two reasons that I think the issue of mobile phones and cancer needs an update on our blog: First, it has been a year and a half since I last wrote about it. At that time I castigated Dr. Ronald B. Herberman, who at that time was director of the University of Pittsburgh Cancer Institute for what I viewed as fear mongering over cell phones and cancer based on at best flimsy evidence. Second, there have been two fairly high profile studies looking at whether there is a link between mobile phone use and cancer. One of these our fearless leader Steve Novella has already discussed, but there was another one that he didn’t see because it didn’t get quite as much publicity, possibly because the corresponding author is based in Korea. I will take this opportunity to discuss them both.
Steve Novella whimsically opined on a recent phone call that irrationality must convey a survival advantage for humans. I’m afraid he has a point.
It’s much easier to scare people than to reassure them, and we have a difficult time with objectivity in the face of a good story. In fact, our brains seem to be hard wired for bias – and we’re great at drawing subtle inferences from interactions, and making our observations fit preconceived notions. A few of us try to fight that urge, and we call ourselves scientists.
Given this context of human frailty, it’s rather unsurprising that the recent USPSTF mammogram guidelines resulted in a national media meltdown of epic proportions. Just for fun, and because David Gorski nudged me towards this topic, I’m going to review some of the key reasons why the drama was both predictable and preventable. (And for an excellent, and more detailed review of the science behind the kerfuffle, David’s recent SBM article is required reading.)
Preface: On issues such as this, I think it’s always good for me to emphasize my disclaimer, in particular:
Dr. Gorski must emphasize that the opinions expressed in his posts on Science-Based Medicine are his and his alone and that all writing for this blog is done on his own time and not in any capacity representing his place of employment. His views do not represent the opinions of his department, university, hospital, or cancer institute and should never be construed as such. Finally, his writings are meant as commentary only and are therefore not meant to be used as specific health care recommendations for individuals. Readers should consult their physicians for advice regarding specific health problems or issues that they might have.
Now, on to the post…
“Early detection saves lives.”
Remember how I started a post a year and a half ago starting out with just this statement? I did it because that is the default assumption and has been so for quite a while. It’s an eminently reasonable-sounding concept that just makes sense. As I pointed out a year and a half ago, though, the question of the benefits of the early detection of cancer is more complicated than you think. Indeed, I’ve written several posts since then on the topic of mammography and breast cancer, the most recent of which I posted a mere two weeks ago. As studies have been released and my thinking on screening for breast cancer has evolved, regular readers have had a front row seat. Through it all, I hope I’ve managed to convey some of the issues involved in screening for cancer and just how difficult they are. How to screen for breast cancer, at what age to begin screening, and how to balance the benefits, risks, and costs are controversial issues, and that controversy has bubbled up to the surface into the mainstream media and public consciousness over the last year or so.
This week, all I can say is, “Here we go again”; that is, between downing slugs of ibuprofen for the headaches some controversial new guidelines for breast cancer screening are causing many of us in the cancer field.
The New York Times has been periodically running a series about the “40 years’ war” on cancer, with most articles by Gina Kolata. I’ve touched on this series before, liking some parts of it, while others not so much. In particular, I criticized an article one article that I thought to be so misguided about how the NIH grant system leads researchers to “play it safe” and how we could cure cancer if we could just fund “riskier” research that I had to write an extended screed about the misconceptions in the article. The latest installment, Medicines to Deter Some Cancers Are Not Taken, also by Kolata, is much better in that it discusses a problem at the heart of cancer, namely that we have developed drugs that can decrease the risk of specific cancers but they are not as widely used as they could be.
The first part of the article contrasts a seeming incongruity:
Many Americans do not think twice about taking medicines to prevent heart disease and stroke. But cancer is different. Much of what Americans do in the name of warding off cancer has not been shown to matter, and some things are actually harmful. Yet the few medicines proved to deter cancer are widely ignored.
Take prostate cancer, the second-most commonly diagnosed cancer in the United States, surpassed only by easily treated skin cancers. More than 192,000 cases of it will be diagnosed this year, and more than 27,000 men will die from it.
And, it turns out, there is a way to prevent many cases of prostate cancer. A large and rigorous study found that a generic drug, finasteride, costing about $2 a day, could prevent as many as 50,000 cases each year. Another study found that finasteride’s close cousin, dutasteride, about $3.50 a day, has the same effect.
This is indeed a contrast. Think about it. Millions of Americans take statins, for instance, to lower their cholesterol and thereby try to prevent the complications of elevated cholesterol, such as heart disease, vascular disease, and strokes. Yet, for at least two common cancers, there are proven effective drugs that will lower the risk of cancer considerably with a side effect profile at least as favorable as that of statins.
I see that the kerfuffle over screening for cancer has erupted again to the point where it’s found its way out of the rarified air of specialty journals to general medical journals and hence into the mainstream press.
Over the last couple of weeks, articles have appeared in newspapers such as the New York Times and Chicago Tribune, radio networks like NPR, and magazines such as TIME Magazine pointing out that a “rethinking” of routine screening for breast and prostate cancer is under way. The articles bear titles such as A Rethink On Prostate and Breast Cancer Screening, Cancer Society, in Shift, Has Concerns on Screenings, Cancers Can Vanish Without Treatment, but How?, Seniors face conflicting advice on cancer tests: Benefit-risk questions lead some to call for age cutoffs, and Rethinking the benefits of breast and prostate cancer screening. These articles were inspired by an editorial published in JAMA last month by Laura Esserman, Yiwey Shieh, and Ian Thompson entitled, appropriately enough, Rethinking Screening for Breast Cancer and Prostate Cancer. The article was a review and analysis of recent studies about the benefits of screening for breast and prostate cancer in asymptomatic populations and concluded that the benefits of large scale screening programs for breast cancer and prostate cancer tend to be oversold and that they come at a higher price than is usually acknowledged.
For regular readers of SBM, none of this should come as a major surprise, as I have been writing about just such issues for quite some time. Indeed, nearly a year and a half ago, I first wrote The early detection of cancer and improved survival: More complicated than most people think. and then followed it up with Early detection of cancer, part 2: Breast cancer and MRI. In these posts, I pointed out concepts such as lead time bias, length bias, and stage migration (a.k.a. the Will Rogers effect) that confound estimates of benefit due to screening. (Indeed, before you continue reading, I strongly suggest that you go back and read at least the first of the aforementioned two posts to review the concepts of lead time bias and length bias.) Several months later, I wrote an analysis of a fascinating study, entitling my post Do over one in five breast cancers detected by mammography alone really spontaneously regress? At the time, I was somewhat skeptical that the number of breast cancers detected by mammography that spontaneously regress was as high as 20%, but of late I’m becoming less skeptical that the number may be somewhere in that range. Even so, at the time I did not doubt that there likely is a proportion of breast cancers that do spontaneously regress and that that number is likely larger than I would have guessed before the study. Of course, the problem is that we do not currently have any way of figuring out which tumors detected by mammography will fall into the minority that do ultimately regress; so we are morally obligated to treat them all. My most recent foray into this topic was in July, when I analyzed another study that concluded that one in three breast cancers detected by screening are overdiagnosed and overtreated. That last post caused me the most angst, because women commented and wrote me asking me what to do, and I had to answer what I always answer: Follow the standard of care, which is yearly mammography over age 40. This data and these concerns have not yet altered that standard of care, and I am not going to change my practice or my general recommendations to women until a new consensus develops.
I have often mused about the difference between being right and being influential – especially in light of the relative success of the anti-vaccine movement. Despite the fact that there is no evidence for a link between vaccines and autism, celebrities like Jenny McCarthy have manufactured public mistrust in one of the safest, most cost effective means of combating disease known to humankind.
So if scientists are not persuading the public with appeals to carefully designed trials and factual data, how should they make their point? I’m not sure I have the full answer, but I think I might have struck a nerve with the public lately. I decided to try a novel approach to communicating my concerns about pseudoscience on the Internet – and presented 20 slides at 20 second intervals to a conference of ePatients in Philadelphia. I did it with powerful and humorous images, tied together with a long Limerick. Sound kooky? Maybe so… but it resonated, and was received with cheers and applause. Now that’s how we like science to be recognized! (more…)