Cancer screening: A modest proposal for prevention

TO CUT IS TO PREVENT

Currently, we offer prophylactic surgery to patients at high risk of cancer. For example, women with BRCA1/BRCA2 mutations are offered prophylactic mastectomy as one of several options for reducing risk of breast cancer. In 2013, the first case of prophylactic prostatectomy was performed in a man who had a BRCA1/BRCA2 mutation. Total colectomy is considered in men and women who have hereditary nonpolyposis colon cancer, instead of segmental resection, to prevent future cancer.

If prophylactic surgery were extended to the general population, it would greatly reduce the number of cancer deaths. Assuming that removing an organ almost always precludes development of cancer, we may predict that prophylactic mastectomy, prostatectomy, or colectomy would save the lives of most of the patients who are still dying of cancer of these organs. The effectiveness rates would approach, but not reach 100%; such is the case with prophylactic mastectomy.

Consider prostate-specific antigen (PSA) screening. Even using the favorable estimate of the impact of PSA screening, arising from the European Randomised Study of Screening for Prostate Cancer trial, 27 men have to be diagnosed, most undergoing local therapy (the trial was conducted before active surveillance became routine), to avert 1 death from prostate cancer over 13 years.⁹

Contrast this “number needed to diagnose” with the number needed to treat for a strategy of routine prostate removal at age 45 or 50. Given that the lifetime risk of death from prostate cancer approaches 3%, and few cases arise before this age, a prophylactic surgical strategy would avert 1 death per 33 operations. If proponents of screening are willing to accept a number needed to diagnose of 27 over a 13-year interval, they may be willing to consider a number needed to treat of 33 over a lifetime.

There may be harms such as perioperative and postoperative complications. Mastectomy could lead to emotional stress from altered body image. Prostatectomy can have long-term complications such as urinary incontinence and sexual dysfunction. Nevertheless, prophylactic organ removal would save far more lives than current screening practices. It also could decrease mental burden, as patients could rest assured that they will never develop cancer, whereas screening often involves ambiguous test results, follow-up tests, and interventions, increasing patient anxiety.

FINDING THE BALANCE BETWEEN BENEFITS AND HARMS

In truth, we do not really advocate universal mastectomy, prostatectomy, and colectomy to prevent cancer, no more than Swift¹ really wanted to eat the children of Ireland to alleviate poverty and famine in that country.  Rather, we use it as an extreme proposal to highlight the scope and depth of harms that inevitably arise from screening.

If proponents of aggressive screening believe that the goal is to reduce cause-specific mortality as much as possible, giving little weight or consideration to overdiagnosis and overtreatment, then they ought to embrace universal prophylactic surgery as well. Recognition of this logical consequence reminds us that we must make screening recommendations that balance benefits and harms.

Considering an extreme perspective can help in recognizing our bias toward saving lives from cancer and discounting the harms. Aggravating this bias, it is impossible to know whether an individual patient has avoided fatal cancer or undergone unnecessary treatment. Moreover, changing practice is more difficult if it involves rolling back interventions that were once the standard.

Balancing benefits and harms is especially difficult when trying to compare the benefit of preventing a single cancer death against a harm that is less serious but more common. Medicine has always involved difficult trade-offs, as seen in cost-benefit analysis of new treatments or balancing quality of life with quantity of life in a single patient. In addition, each individual may place different values on benefits of screening and avoiding possible harms.

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. We must proceed with caution when subjecting large numbers of men and women to the possibility of psychological burden and decreased quality of life.

Given the growing appreciation of the harms of screening, it is likely that future guidance will continue to move toward less- frequent screening or focusing resources on high-risk populations, where the absolute magnitude of benefit is greater. Cancer screening is also likely to become an individual decision based on personal values and informed decisions.