Screening Can Do Silent Harm Part II

An unplanned follow-up to last week's post

I was pretty proud of my post last Friday, Screening Can Do Silent Harm. I described five cases that demonstrated the silent harms of screening. Unfortunately, unless you were both REALLY clued into the potential harms of screening AND basically live inside my head, the post left something to be desired. Reactions on twitter and in the comments were well-represented by these two:

“It’s an odd article as people not already in the know won’t realise what it’s about!”

“It does seem a bit like an article that only people who are already experts… will understand... I was waiting for the revealer final sentence that never came… Just needed that final sequence where you realize he was John Connor's father.”

My own wife – by far the smartest, most sensible doctor in my house -- asked if I had forgotten to add something.

So, if you haven’t read last week’s piece, go back and read it. Then read what follows, I hope this will make my point more clear.

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The successes of screening are loud.

May Smith is a 50-year-old who has a colonoscopy. A 1.5 cm adenomatous polyp with a focus of adenocarcinoma is discovered. She goes back for a follow-up exam and there is no remaining cancer. The colonoscopy may have saved her life. It at least saved her from a later diagnosis of a larger cancer that would have required more extensive therapy.

Anne Picard is 55-year-old woman who gets yearly mammograms. This year, an area of asymmetry and macrocalcifications are found. Biopsy reveals ductal adenocarcinoma. She is cured with lumpectomy and XRT. Genetic testing -- she had a maternal aunt with breast cancer -- shows her to have a BRCA-2 mutation. This gives important information for her and her daughter.

John Connor is a 65-year-old man who gets a yearly PSA. This year, the PSA jumps from 3 to 10. Biopsy reveals Gleason’s 4+4=8 prostate cancer. He undergoes curative prostatectomy. He is left with mild ED, well-managed with medications.

People who have experiences like these feel like cancer screening was beneficial, if not lifesaving. Many of them become advocates for screening. The truth, however, is that successes are relatively rare. Here are some nice infographics about mammography, prostate cancer screening, and data for colonoscopy. Even apparent successes are often not what they seem and screening can also cause harm.

• There is a very small chance a person can be harmed directly by the screening test or negative, downstream, confirmatory tests.

• People suffer from anxiety related to the test and the results. This anxiety will be especially irksome if the result is a false positive.

• Screening tests can lead to overdiagnosis, the diagnosis of a cancer that does not need to be treated. (See the links above. The chance of this is about 6/1000 for 10 years of mammograms).

• Many of our screening tests have only been shown to decrease disease specific mortality, not overall mortality. The tests change what you die from, not when you die.

• Some patients are diagnosed with a cancer that requires treatment but not treatment in the preclinical stage. This means a patient would have had the same outcome if she had only been diagnosed when symptoms developed, rather than earlier, with screening. In this case, the only thing that screening has done is make the person live longer as a cancer patient.

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Last Week’s Cases

Nick Arroyo was harmed by screening that did nothing but extend his life as a cancer patient. This case is the story of lead time bias. A screening test prolongs survival with the disease without prolonging life or decreasing mortality. You know you have the disease for longer, and suffer the consequences of being a patient during this time. The data for lung cancer screening are especially weak.

Joan Drake was harmed by a non-indicated screening test. We don’t screen for coronary disease. This seems counter-intuitive, why would we not screen for our biggest killer? We don’t because study after study has shown that screening increases diagnosis, increases treatment, but does not change outcomes. Joan would have danced at the wedding, without a stent, and without the worry that she might fall and hemorrhage given her post procedure need for aspirin and ticagrelor.

Prostate cancer screening is about as difficult an issue as there is. Andrew Kennedy’s experience mirrors that of so many men I have cared for. Our ability to risk stratify men with an elevated PSA has improved over the years. Many men with an elevated PSA can now be monitored, rather than subjected to treatment with surgery or radiation. However, many men (or their families) just can’t tolerate the idea of not treating a “cancer.” They will choose treatment rather than watchful waiting or expectant management (or whatever we choose to call it these days¹). Despite the advances in treatment, lasting harm is still common.

What was Nan Williams supposed to do? We find a disease that may or may not progress to cancer. Ms. Williams’ doctor might tell her that 15-50% of DCIS will progress to cancer. More likely her doctor will tell her that she is fortunate that we picked up breast cancer in its earliest stage. Because we can’t tell her if her DCIS is likely to progress, we must treat it like it is cancer. Cognitive dissonance requires her to celebrate the medical success.

Like Ms. Drake, Bill Delgado had a screening test that nobody recommends. The USPSTF give peripheral artery disease screening a level I (“I” as in insufficient evidence). Why was it offered? An optimist would say that someone thought it might help and couldn’t possibly cause harm. A skeptic would say that a vascular surgery department was hoping to generate business. In Bill’s case, nothing changes in his management except that a stable, productive, patient-doctor relationship is poisoned. Sure, maybe the doctor could have done a better job in the follow-up visit, but do we really need to stress test the overworked, underpaid primary care physician?

I am neither for nor against cancer screening. What I am against is the reflexive belief that screening is beneficial. Sometimes it is, sometimes it is not. Screening is a medical intervention performed on healthy people, and like all similar interventions, should be undertaken with eyes wide open. I am pretty sure we save thousands of people each year with screening tests. I am also sure that we falsely reassure some people by telling them that they do not have disease when they do. We put people through diagnostic testing after false positive tests that they would not have needed had they not been screened. And, in some people, we diagnose and treat a disease that would never have caused them harm.

If you want to go a little deeper on the topic of screening, I have written a number of posts on Sensible Medicine about screening. This one is a primer on the characteristics of a successful screening test. There is a three part series (one, two, and three) titled “I Am Afraid of Early Cancer Detection.” We even had a video podcast debate about colon cancer screening. I am the biggest proponent of screening in the debate (and, by the way, I wipe the floor with my colleagues).

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Wait, one more thing. We have merch, well actually just t-shirts.

For the past year we have given away a few t-shirts to some “friends of Sensible Medicine”. After VP starting wearing one in videos like this one, we’ve had surprising demand for them. Because I am getting sick of making runs to the post office to mail them, we have set up a way that anyone can buy one. There is also a link on the about page. They are pretty cool, wear them proudly!

1. The progress in the language reminds me of George Carlin’s great sketch about euphemisms.