The study found that the score had an accuracy of 82 percent in predicting 15-year survival, Scardino said. "If you could predict what would happen in the stock market in the next 15 years with 82 percent accuracy, you would be a genius," he said.
Overall, there was a greater chance that a man in the study would die of a cause other than prostate cancer. The rate of death from other causes was 38 percent, compared to 12 percent attributed to prostate cancer.
The new predictive method will be made public soon, after medical review, so that physicians and men can learn about their anticipated survival after surgery, Scardino said.
"Any person can look at it and put in the numbers," he said.
The new predictive tool is an improvement over the existing method, which relies essentially on readings of prostate-specific antigen levels, Stephenson said.
But no such predictive method exists for newly diagnosed men who must chose between treatment and watchful waiting, and so the study presents a predicament for those men and their physicians, he said.
"It questions the lethality of prostate cancer," Stephenson said. "Perhaps a similarly low risk might have been seen if the men did not have prostatectomy. We can't say whether a cancer poses enough of a threat to the patient so that therapy is needed."
Prostate cancer surgery is not free of problems, Stephenson said. Its major side effects are incontinence and loss of sexual function.
Many prostate cancers grow slowly -- so slowly that an old medical byword is that "more men die with their prostate cancer than of it." No existing method can single out the cancers that will be fatal if left untreated.
"We really need better tools for really identifying prostate cancers that pose a threat to longevity," Stephen
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