https://www.telegraph.co.uk/news/2018/03/06/prostate-screening-saves-no-lives-may-do-harm-good/It was mentioned on R4 Today Programme yesterday and is summarised in the Telegraph - link above.
The basic problem is that the blood test (PSA) can come back positive for a variety of reasons other than cancer, and unfortunately also be negative when there is actually early cancer.
False positive results could lead to invasive further testing which can actually harm the patient (infection, long term pain, incontinence, impotence). False negatives clearly cause failure to diagnose.
The other point is that the tests don't give any information on the potential of the cancer to threaten life. There was always the adage that most men die with prostate cancer than than from it.
The intended and proper use of the PSA test is as a tumour marker, ie to track the progression of a cancer or the effectiveness of its treatment.
The current advice is to see a doctor if you have symptoms, eg poor flow, dribble at the end, getting up several times at night or taking a while to start.
Clearly if you've got a strong family history then getting checked out makes sense too. Ethnicity comes into it with black people being higher risk.
If you're ok with the uncertainty in the blood test results, then most doctors are happy to do the PSA. A low level would be 'reassuring' but not conclusive. A markedly raised level would be concerning but most patients with highly raised levels are symptomatic.
The grey area in the middle is what causes the problems.