We are hopefully witnessing an important turning point in the way people think about cancer.
Thirty or so years ago, the public was promised that a “cure for cancer” was imminent. That was before all the powerful biological techniques of today made it clear that “cancer” is not a simple, single disease, but instead a catch-all term for uncontrolled cell growth that has many different forms and occurs in many different contexts. Indeed, trying to find a genuine cure for cancer may be similar to trying to find one for the common cold, which exists in too many forms to make such a search practical.
Just as with colds, prevention is the best strategy, because effective treatment, though there have been a few resounding successes, remains so elusive. And yet the money in cancer research may always be more in the testing of new treatments, which is supported a lot by private industry, rather than in learning more basic biology about different types of cancer themselves, which will only be funded by the government. Not only do we need to learn more about what prevention strategies might be effective, but (perhaps in the shorter term) how to better target treatment, and especially whether to treat at all.
The fact that we don’t really know yet which early cancers detected by screening will develop into full-blown disease is the elephant in the room whenever screening is questioned as a cancer-treatment strategy. An individual facing a positive breast or prostate small cancer screen cannot yet be consoled with the absolute knowledge that the particular cancer they have is unlikely to progress, despite the fact that it is now clear that the majority of such cancers do not. But we do have information that should provide ample justification for any healthy person to make the informed decision that he or she does not wish to be screened.
First, current research (Esserman et al., 2009) finds that breast and prostate cancer rates are indeed rising, but that this rise is attributable to more small, asymptomatic cancers being found via mammography and the PSA test. The rate of metastatic cancers, i.e. those that cause death, has not declined. This suggests strongly that the only thing that screening of healthy people has accomplished is to reveal cancer rates that were already high, causing a lot of angst and unpleasant – and sometimes quite damaging – treatment.
Second, very few deadly cancers are found by screening, because the deadliest progress very quickly, and probability dictates that screening once a year is very unlikely to “catch” them. This means that unless you increase screening rates to something like once a month, screening will never be a useful tool for finding the cancers most likely to kill. And given that the probability for a specific individual getting one of those aggressive cancers is relatively low, the burden of screening would simply be prohibitive for both the individual and the system, in both time and money. Furthermore, finding an aggressive cancer early is no guarantee that it will be “cured,” because the most aggressive are also the most difficult to check through current treatments.
So, despite our inability to sort out the “benign” cancers from the aggressive ones, there are multiple reasons for us to try to alter the culture of breast and prostate cancer screening, because the prevailing belief that all cancer must be destroyed immediately is frankly costing us a lot in blood and treasure. The truth that the medical culture must be reformed to understand is that everybody has cancer cells in their body, but these only progress to be invasive in a small subset of the population.
The tendency is to think of screening as a “prevention” strategy in the first place, rather than as “treatment,” which it becomes for a lot of people, is a major reason we have the problem today in which lots and lots of small cancers are found through screening, most of which will never cause harm to the person. Dr. H.G. Welch brilliantly illuminated this problem (and those outlined above) in his 2004 book, “Should I Be Tested for Cancer?” in which he pointed out five years ago that a general fear of cancer and the promotion of screening as a “prevention” strategy create a vicious cycle of more and more screenings finding more and more cancers. More (asymptomatic) people are diagnosed through screening, increasing our awareness of an “epidemic” of cancer, which causes more promotion of screening for the general population, many of whom get screened, and thus diagnosed.
This is only one of the problems in the current cancer culture. Everybody who does not have cancer should read Dr. Welch’s book now, because cancer screening is a complex problem that does not lend itself to sound-byte reporting do’s and don’ts. (Just read the comments on this health blog entry on cancer screening from the New York Times, and it is clear that news outlets simply aren’t up to the task.) Thus, although it is a huge breakthrough that the American Cancer Society is finally admitting the problems associated with excessive screening, changing the cancer culture will be a long and difficult hill to climb – especially with other organizations still sending the conflicting message that everybody needs to get screened, now.
A somewhat discouraging take-home message from Welch’s book is that most doctors are not well informed about the downsides of cancer screening (although it is certainly true that muddying the waters further is overly defensive medicine through fear of lawsuits). This is because although you might assume that doctors are trained scientifically and understand numbers and statistics well, shockingly few of them do. Dr. Welch is one of them, thankfully, and through his expertly and clearly written book, you can be too.
Hopefully, we really are undergoing a sea change about how we think about cancer, and that this will lead us in more productive research directions, such as who should actually receive particular treatments, and who should not. But in the meantime, resisting the urge to package the benefits – but not risks – of cancer screening to a pink political campaign, and instead thinking logically about what the cancer screening numbers really mean, would result in a lot better health care.
Esserman L., Shieh, Y. and Thompson, I., 2009. Rethinking screening for breast cancer and prostate cancer. Journal of the American Medical Association 302:1685.
Welch, H.G., 2004. Should I Be Tested for Cancer?: Maybe Not and Here’s Why. University of California Press, Berkeley, CA.