Biology in the News Explained

PSA screening test is still uninformative

A common thread here is on screening, and what cancer screening tests are actually useful.  We have an unfortunate situation now in which someone develops a new easy-to-do test that they think is good for screening because those with the cancer in question have been found usually to show a particular result from the screening test.

This result looks useful, so everyone starts recommending the test – not only doctors, but well meaning nonprofit organizations devoted to preventing/curing this-or-that type of cancer.  Unfortunately, the rush to promote screening ignores two major problems.  The first problem is that the screening results are looked at only in one direction, and faulty logic is used to argue that the result is useful.  That is:  cancer patients all get result X on a screening test.  Therefore, if you get result X on the test, you likely have cancer that needs to be identified and treated right away.

The second problem is that those people who get result X, get further testing, are found to have cancer, and are treated, all come out of treatment praising the screening test for saving their lives.

The first is a problem because of the obvious yet continuing logical mistake that if cancer means result X, then result X means cancer.  It ignores the possibility that people with cancer are just a subset of the people who get result X on a test, and that there is actually a way to distinguish which subset that is without conducting a further, much more invasive test.

The second is a problem because although scientifically we understand enough now to know that aggressive, life-threatening cancer is only a subset of all the different types of cancer there are, there is a huge cultural lag in this knowledge, even when it comes to conversations between doctors and their patients.  Because historically, we had no screening tools, the only cancers known were the symptomatic and usually deadly ones.  Doctors resorted to drastic means to curtail them, such as radical mastectomies, which drastically reduced quality of life and which we now know to be overkill.  Thus, we have the compounding problems that we can now find tiny cancers through screening, most of which we never would have known existed thirty years ago, we have witnessed a big propaganda push for cancer screening (most notably for prostate and breast cancers), and we still think we need to treat them all.

Unfortunately, it’s clear that for some of the best known cancers, more screening means more cancer diagnosed, most of which is still harmless.  This has been one of the reasons for a jump in cancer diagnoses since the 1970s, and an even bigger jump in survival rates (as more and more harmless cancers are discovered, “survival” rates will go up, and be touted as wonderful medical advances).  (Of course there may indeed be environmental and other reasons for more cancer diagnoses, and chances are they all play a role; but screening clearly does too.)

Prostate exam

A more accurate test for cancer

The prostate-specific antigen test is notorious for its high level of false “positive” results – meaning that although men with prostate cancer usually have a heightened PSA, many, many other men have a heightened PSA for a lot of other reasons.  Our overzealous “war” on prostate cancer in particular has been devastating to the quality of life of millions of men:  it has been estimated that 48 men are treated to save one life from prostate cancer (for women and breast cancer, the ratio is closer to 10 to 1).  At best, this is contributing to our unsustainable rise in healthcare costs.  At worst, it demonstrates we are still essentially bleeding people with leeches.

Unfortunately, it is psychologically (and economically, from the point of view of profit-making drug and device companies) a lot easier to get people to try a new screening or treatment than to get them to stop using one that doesn’t work.  This means the cultural lag behind the science will continue, and more people will needlessly suffer from painful biopsies and cancer-diagnosis-induced pain and stress.

It’s hard to walk two steps down a street without hearing about benefits of screening (which are often overblown as it is by organizations that benefit from it).  What everyone without a current cancer diagnosis needs to do is better understand the risks of screening, and the best way to do that is by reading this book:  Should I Be Tested for Cancer?: Maybe Not and Here’s Why.  It will help you work with your doctor to make a rational decision regarding screening.  Our tools for detecting and understanding cancer have changed dramatically in the last few decades; it’s time to change our cultural attitude about it just as dramatically.

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