Dear Editor,

With great interest, we have read the results of the ProtecT-trial, comparing radical prostatectomy, radical radiotherapy, and active monitoring [1, 2]. A number needed to treat (NNT) of 27 and 33 for prostatectomy and radiotherapy are stated, respectively, to prevent one patient developing metastases. The authors mention the effect of selection due to PSA-testing compared to the PIVOT and SPCG-4 trial and the advancements in treatment of nonprostatic disease. However, it might be the case that the NNT will drop with further follow-up due to this stage migration to lower risk disease. This lead-time bias has also been observed in subsequent reports of the ERSPC trial [3–5] (NNT/number needed to detect (NND) of 48 at 9 years, 37 at 11 years, and 27 at 13 years for one prostate-cancer death).

Furthermore, selection could indeed be improved with multi-parametric MRI, and treatment techniques are evolving, as stated. However, treatment-related side effects remain substantial [2]. The considerable probability of radical intervention in the active monitoring group might pave the way for tissue-preserving techniques if differences in effectiveness are so minor.