Predicting clinically significant prostate cancer

Current evidence suggests that screening men for prostate cancer is a double-edged sword, say Dr Carvell T Nguyen and Dr Michael W Kattan, both working in urological institutes in Cleveland, Ohio, in the US. The researchers say the ethical and economic implications of over-diagnosis and over-treatment of clinically insignificant prostate cancer are profound.

Men with 'indolent cancers' presumably would not benefit from active treatment and may suffer significant harm, such as impotence and incontinence, as a result of complications. The scientists question the cost-effectiveness of current screening regimens.

Writing in the Asian Journal of Andrology, Nguyen and Kattan say conventional testing – the PSA test – has improved the early detection of prostate cancer, leading to more men being diagnosed and treated. Yet this has not resulted in improved survival rates, and may actually cause harm.

They note that the increased incidence of prostate cancer includes a large number of indolent tumours that do not pose a significant health threat and do not require treatment.

Because of the difficulty in measuring relevant end points related to lethal prostate cancer, medical specialists depend on prediction models to estimate the likelihood of clinically insignificant disease.

The researchers say these models have high accuracy identifying organ-confined disease but this does not necessarily preclude the possibility of cancer progression in untreated patients. As well, the models have a 10% to 20% rate of misclassification and their use does not completely exclude adverse pathologic features at the time of diagnosis.

Nevertheless, although imperfect, the models currently do offer the best estimates of the likelihood of having clinically insignificant prostate cancer.

“Combined with clinician expertise and patient preference, these risk estimates can form the basis of truly informed decisions regarding the need for immediate intervention versus active surveillance, potentially mitigating some of the problems associated with the contemporary over-diagnosis and over-treatment,” the researchers say.

“Because of this overtreatment phenomenon, active surveillance with delayed intervention is gaining traction as a viable management approach in contemporary practice.

“The ability to distinguish clinically insignificant cancers from those with a high risk of progression and-or lethality is critical to the appropriate selection of patients for surveillance protocols versus immediate intervention.”