Is Breast Cancer Screening Worthless? The Fact Box Speaks
By Bryan Caplan
Gigerenzer’s Risk Savvy also presents transparent statistical evidence against routine mammograms. The presentation slightly changes, relying on a “fact box” rather than an icon box. But the idea remains the same: Clearly summarize outcome frequencies from women randomly assigned to either screening or no screening. Results:
At first glance, screenings save the life of one women in a thousand. On closer look, however, screenings only alter the kind of cancer that kills you, not overall cancer mortality. Whether they’re screened or not, 21-in-1000 women died of cancer within ten years.
Details on the benefits:
First, is there evidence that mammography screening reduces my chance of dying from breast cancer? The answer is yes. Out of every one thousand women who did not participate in screening, about five died of breast cancer, while this number was four for those who participated. In statistical terms that is an absolute risk reduction of one in one thousand. But if you find this information in a newspaper or brochure, it is almost always presented as a “20 percent risk reduction” or more.
Second, is there evidence that mammography screening reduces my chance of dying from any kind of cancer, including breast cancer? The answer is no…
In plain words, there is no evidence that mammography saves lives. One less women in a thousand dies with the diagnosis breast cancer, but one more dies with another cancer diagnosis. Some women die with two or three different cancers, where it’s not always clear which of these caused death.
Details on the costs:
First, women who do not have breast cancer can experience false alarms and unnecessary biopsies. This happened to about a hundred out of every thousand women who participated in screening… Second, women who do have breast cancer, but a nonprogressive or slowly growing form that they would never have noticed during their lifetimes, often undergo lumpectomy, mastectomy, toxic chemotherapy, or other interventions that have no benefit for them…
Furthermore, since diagnosis typically leads to treatment, the fact that more-diagnosed women don’t live longer is striking evidence that breast cancer treatments are, on average, ineffective. Hansonian medical skepticism may be overstated, but it is firmly grounded in fact.