LONDON — The longest study yet on prostate cancer testing provides more evidence that getting screened doesn't cut the chances of dying from the disease. In a 20-year study of more than 9,000 Swedish men, researchers found no difference in the rate of prostate cancer deaths between the men who were periodically screened and those who weren't.

Routine screening for prostate cancer is controversial and the new results aren't likely to end the debate about the value of testing. Critics say screening leads to unnecessary biopsies and treatment with little proof that it saves lives.

Testing is done with a physical exam and a PSA blood test. "There is no escaping the fact that we need a better tool … to help detect prostate cancers that actually need treating, as opposed to innocent ones that do not," said Malcolm Mason, a prostate cancer expert at Cancer Research U.K. in a statement.