Re: PSA screening - what is the NNT (number needed to test)?
The NNT figures given by Dr de Lemos should be taken with a
pinch of salt. The assumption is made that the patients with screening
detected prostate cancer who are selected for treatment will die of
prostate cancer if not treated. This is not necessarily the case,
particularly for the majority who develop the disease in later life. As Dr
De Lemos suggests there is wide uncertainty as to the true NNT. This is
due largely to the uncertainty of the true benefit of radiotherapy and
prostatectomy. Randomised trials were previously difficult due to the long
follow-up period required and firm beliefs of surgeons or radiotherapists
regarding their own modalities. Now randomised trials are difficult due to
increasing pressure towards treatment rather than 'watchful waiting'
Inevitably, with screening more patients will be exposed to the side-
effects of these treatments and the NTP (number treated pointlessly) will
Competing interests: No competing interests