Dr. Klein weighed in with the view that on balance, the patient population is currently better served by immediate treatment.

“Many patients are overtreated as a result of the use of immediate treatment. But the problem with active surveillance is that current tools do not allow us to distinguish between biologically indolent tumors and biologically aggressive tumors—except for those in the latter category that are of the highest Gleason grades,” he said.

He also pointed out that there are no validated ways to monitor for tumor progression in men who are managed with surveillance. For example, in the Johns Hopkins study, “neither PSA nor any of its derivatives—percent free PSA, PSA density, PSA velocity, or PSA doubling time—were able to distinguish men who progressed to more aggressive tumors on biopsy from those who didn’t.”

Another strike against active surveillance, he said, is shown by the fact that in the Johns Hopkins study, “20% of the men who delayed prostatectomy by two years then had incurable disease.” In addition, in the Canadian study led by Dr. Klotz, “two thirds of the men who underwent prostatectomy after disease progression [detected by active surveillance] had extraprostatic disease. Better tools are needed to identify who may be safely watched and to know when it’s time to proceed with therapy to prevent life-threatening progression.”

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Commenting on the debate, Dr. Klotz pointed out that six published studies involving more than 1,800 patients indicate that, in the intermediate term at least, active surveillance is safe. He noted that the correct approach will be clarified in coming years.

“These two presentations by very thoughtful and well-informed experts in the field underscore both the appeal of active surveillance and the limitations of our knowledge,” Dr. Klotz said.

“The benefits of avoiding radical treatment are obvious, while the risks are somewhat less so.… As the data mature, confidence in the safety of surveillance is likely to grow. Longer follow-up and successful completion of the large-scale, randomized trials currently under way will be critical to resolving the uncertainty regarding the risks of surveillance, which at this point in time appear modest.