Tradeoffs in cancer screening: Where do we draw the line?

March 14th, 2019

It’s not a secret that cancer screening tests aren’t perfect. Tests such as mammograms, colonoscopies, and PSAs (prostate-specific antigen test) have high rates of false positives and risk of overtreatment. For example, for every 10,000 women in their 40s who get annual mammograms, three fewer will die of breast cancer in ten years, but 6,130 will have a false positive test, 700 will receive an unnecessary biopsy, and there will be no reduction in all-cause mortality.

However, it’s difficult to accept the idea that by screening less, we may be risking lives. As a patient, nothing seems scarier than dying of cancer, so a false positive seems harmless in comparison. Why would we trade off potential lives saves in exchange for a few “false alarms”? Many doctors share this sentiment. “Yes, there are false alarms, but if potentially saving your life is more important to you than transient anxiety from a recall, start at 40,” one cancer radiologist wrote on Twitter

The question is, where do we draw the line? False positives are not harmless. They not only create stress but also can lead to painful biopsies, radiation, or other complications. If it is worth exposing 6,130 out of 10,000 women to false positives to save three lives from cancer (with no change in all-cause mortality), then why don’t we screen all women starting at age 30? Or screen every six months?

In a new commentary in the Cleveland Clinic Journal of Medicine, Dr. Myung Kim, Dr. Go Nishikawa, and Dr. Vinay Prasad use a radical thought experiment to discuss the question of where to draw the line in cancer screening. Kim et al. offer a “modest proposal” for those who believe that cancer prevention outweighs any harms: If we believe that preventing one cancer death is worth any number of lesser harms, then we should recommend that all people have their breasts, prostate glands, and colons removed.

Sounds crazy, but as the authors point out, and we already offer this surgery to patients at high risk of breast cancer, and removing organs would certainly go a long way to preventing cancer from occurring. For example, it takes diagnosing 27 people with prostate cancer with PSA screening over 13 years to prevent one prostate cancer death. Why not remove everyone’s prostate, which would save one person’s life for every 33 surgeries?

The author’s outlandish proposal is not meant seriously, but it makes an important point. “There is an undeniable trade-off with screening, and we must make a conscious decision on where to draw the line when harms outweigh the benefits,” they write. “We must proceed with caution when subjecting large numbers of men and women to the possibility of psychological burden and decreased quality of life.”