Many cancer screening tests do not improve longevity, but some still 'may be worthwhile'

Key takeaways:

• Many common cancer screening tests do not appear to increase patients’ longevity.
• Sigmoidoscopy, used to screen for colorectal cancer, was the only test with a significant lifetime gain, at 110 days.

With the exception of sigmoidoscopy, common cancer screening tests do not appear to extend patients’ lifetimes, according to the results of research published in JAMA Internal Medicine.

Many advocate for cancer screening as a way to save lives and increase longevity, Michael Bretthauer, MD, PhD, a professor at the University of Oslo in Norway, and colleagues wrote. However, like all medical interventions, cancer screening includes benefits and harms — for example, bleeding and perforation during colorectal cancer screening.

Therefore, cancer screening tests could reduce cancer-specific mortality and simultaneously fail in increasing longevity “if the harms for some individuals outweigh the benefits for others or if cancer-specific deaths are replaced by deaths from competing causes.”

“It is important to provide the public with reliable estimates for benefits and harms of screening on cancer incidence and mortality and on lifetime gained by screening,” Bretthauer and colleagues wrote. “While the former has become standard for most cancer screening tests, the latter goal is still difficult to assess.”

Therefore, the researchers conducted a meta-analysis of randomized clinical trials to estimate the lifetime gained with cancer screening tests.

They searched the MEDLINE and Cochrane library databases for randomized clinical trials with more than 9 years of follow-up that reporting all-cause mortality and evaluated the lifetime gained for several common cancer screening tests: colonoscopy, sigmoidoscopy or fecal occult blood testing (FOBT) for colorectal cancer; CT screening for lung cancer in smokers and former smokers; prostate-specific antigen testing for prostate cancer and mammography screening for breast cancer. They ultimately included 2,111,958 participants.

Bretthauer and colleagues found that common cancer screening tests do not save lives by extending a patient’s lifetime, except for maybe sigmoidoscopy to screen for colorectal cancer. That was the only screening test with a significant lifetime gain: 110 days (95% CI, 0-274 days).

There did not appear to be significant differences following other screening tests. The differences were:

• 0 days for mammography (95% CI, –190 to 237);
• 0 days for FOBT screening (95% CI, –70.7 to 70.7);
• 37 days for colonoscopies (95% CI, –146 to 146);
• 37 days for prostate cancer screening (95% CI, –37 to 73); and
• 107 days for lung cancer screening (95% CI, 286 to 430).

Bretthauer and colleagues emphasized that, despite the results, “some individuals prolong their life due to these screening tests.”

“We do not advocate that all screening should be abandoned,” they concluded. “Screening tests with a positive benefit-harm balance measured in incidence and mortality of the target cancer compared with harms and burden may well be worthwhile.”