Pacala stressed, however, that decisions on whether to screen for or treat a disease should not be based solely on a number. He said longevity estimates should be used to facilitate discussions between doctors and patients.
A doctor not involved in the study agreed.
"There is absolutely a need for better tools for understanding life expectancy," said Dr. Ethan Basch, an oncologist and director of the cancer outcomes research program at the University of North Carolina School of Medicine, in Chapel Hill.
But no life-expectancy calculator -- or any single guideline -- is enough, Basch said. "This is one piece of information to help an older patient make an informed, rational decision," he said.
Basch chaired the American Society of Clinical Oncology committee that recently developed the group's guideline on PSA screening for prostate cancer. The society suggests that doctors discuss PSA screening with men who are expected to live for more than 10 years.
PSA screening is controversial because prostate cancer is often slow-growing and will never threaten a man's life. Even if screening catches a prostate tumor, many men may be treated unnecessarily.
For a man expected to live fewer than 10 years, the ASCO says the potential harms of PSA screening seem to outweigh the benefits. For men with a longer life expectancy, the group says things are not so clear-cut, and having a conversation with your doctor might be worthwhile.
Learn more about screening tests from the U.S. Preventive Services Task Force.
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