There is a Benefit

The ongoing flap over monitoring for prostate cancers seems to be slowly disappearing except for those who one would guess want to see old men die. The most recent one is in the current NEJM where the study results note:

We randomly assigned 695 men with localized prostate cancer to watchful waiting or radical prostatectomy from October 1989 through February 1999 and collected follow-up data through 2017... Men with clinically detected, localized prostate cancer and a long life expectancy benefited from radical prostatectomy, with a mean of 2.9 years of life gained. 

But they further conclude:

The limitations of our trial are that the analyses according to age were not prespecified in the protocol, were exploratory, and were, among other caveats, sensitive to chance findings and not adjusted for multiple testing. Furthermore, the diagnostic procedures used today differ drastically from those used during the period of enrollment in our trial. As a result of widespread PSA testing today, most men have nonpalpable, PSA-detected tumors, whereas in our trial the majority of the men had clinically detected, palpable tumors. Today, men undergo multiple biopsies or multiparametric magnetic resonance imaging with targeted biopsies, whereas the participants in our trial had only cytologic or sextant biopsies, with few cores investigated as compared with current standards. Today, the clinical domain of localized prostate cancer is different, and the sensitivity for the detection of high-grade cancers during our trial was considerably lower than it is today. In clinically detected prostate cancer, the benefit of radical prostatectomy in otherwise healthy men can be substantial, with a mean gain of almost 3 years of life after 23 years of follow-up.

Namely, the data is old but it demonstrates life saving and with the use of PSA it seem dramatically better.

The data against "watchful waiting" just keeps piling up. As they say; believe them or your lying eyes!