May 29, 2017


All These Cancer Screenings Probably Won't Save Your Life : Millions are suffering through needless and destructive treatments that follow early-detection testing results--and all for cancers that likely wouldn't kill you anyway. (Paul A. Offit, 05.29.17 , Daily Beast)

Some cancers are easy to prevent. For example, sun block can prevent skin cancer; the hepatitis B vaccine can prevent liver cancer; the human papillomavirus (HPV) vaccine can prevent cervical cancer as well as head, neck, anal, and genital cancers; and cessation of cigarette smoking can prevent lung cancer.

Other cancers are harder to prevent, like those of the prostate, thyroid, and breast. The reason, as explained by Gilbert Welch, a professor of medicine at Dartmouth, is best explained using a barnyard analogy. Imagine, writes Welch, that three animals in a barn are trying to escape: a bird, a turtle, and a rabbit. When you open the door, they escape at different rates.

• The bird, which will fly out before you can close the door, is analogous to a cancer that is so aggressive that it will kill you no matter what you do. Even if detected early, it doesn't matter--this cancer is invariably fatal.

• The turtle, which is so plodding that it will never escape, is analogous to a cancer that is so slow growing, so non-virulent that it is never fatal. People die with this cancer, not from it.

• The rabbit, which can be caught if the door is closed quickly enough, is analogous to a cancer worth detecting. If not detected early, this cancer is fatal. If it is detected early, then the screening test will save lives.

Screening tests are valuable only if they are detecting mostly rabbits, like Pap smears to detect cervical cancer or colonoscopies to detect colon cancer. For thyroid, prostate, and breast cancers, however, the value of early screening tests isn't so clear. Atul Gawande, a surgeon at Johns Hopkins University School of Medicine and prolific author, sums it up best: "We now have a vast and costly health-care industry devoted to finding and responding to turtles."

Posted by at May 29, 2017 5:33 AM