Prostate cancer is the UK's most common cancer, causing 55,300 cases and 12,200 deaths each year. Mass screening is used for other major cancers, including breast, bowel and cervical, to detect the disease early, when it is most treatable. But it can also cause harm in the form of overdiagnosis and overtreatment, while using up limited NHS resources.
"It's a head versus heart decision," explained Chiara de Biase, the director of health services, equity and improvement at Prostate Cancer UK. "Your heart is saying 'just screen everybody, let's give everybody a PSA test'. But it's not harmless, and not doing harm is just as important to us as finding cancers."
The committee is almost certain to rule out regular checks for all men over the age of 50, which is how NHS breast screening works for women, as PSA tests are not reliable enough. The most likely outcome is a targeted screening programme for those at the highest risk of prostate cancer due to their ethnicity or genes.
To get the greatest return on screening (in terms of lives saved per test), it makes sense to focus on the men most likely to have cancer. These fall into two broad categories: black men, who are twice as likely to die from prostate cancer; and those with a family history of the disease.
In total there are 8.2 million men aged 50 to 69 in the UK, and about one million of these have a family history of prostate cancer. There are also 375,000 black men aged 45 to 69, who would be eligible for a targeted screening programme based on ethnicity.
"We have always believed that the evidence is strong enough for screening for black men and for men with a family history," said de Biase. "Anything less than that I'd be really surprised and really disappointed. But even a week out, I don't know which way it is going to fall."
Hoy, the Olympic cyclist, who has incurable prostate cancer, has spoken of how his father and grandfather also both had the disease. He has called for more checks for men with a family history.
Charlie Batty, 72, is among hundreds of thousands of men who would have benefited from targeted screening. He was diagnosed last year and has just undergone 37 sessions of radiotherapy after the cancer spread. "My father had also been diagnosed with prostate cancer, and I must confess that I was initially unaware that this meant I had a greater risk myself," he said.
The practicalities of identifying those at high risk are tricky, especially as many GPs still don't hold ethnicity data for patients. Naser Turabi, from Cancer Research UK, said: "Black is a self-reported social category. Do you include mixed race in there? The data is poor. Black is a very diverse genetic category."
However, David James, of Prostate Cancer Research, said that "just because something's difficult doesn't mean we shouldn't do it". He said that any screening programme recommended by the committee would take three to five years to implement, which would be enough "time to incentivise the collection of that data on ethnicity and family history".
Among the one million men with a family history of the disease, there is a subgroup with specific genetic mutation to the BRCA genes who are three times more likely to get aggressive prostate cancer.
This group are at the highest risk of all, and experts believe the NSC may single them out as the first to benefit from targeted NHS prostate screening. Mutated BRCA genes are carried by one in 400 people and increase the risk of breast, prostate and ovarian cancer.
BRCA is often known as the "Jolie gene", as the actress Angelina Jolie had a preventative double mastectomy after discovering she carried the mutation.
Professor Nick James, of the Institute of Cancer Research (ICR) in London, said: "Recent work by the ICR has shown that annual PSA testing picks up more dangerous prostate cancers in men with BRCA1 and BRCA2 mutations than non-carriers, suggesting all men from the age of 40 with these mutations should be offered regular tests."
Tony McHale, 74, found out he had a mutation to the BRCA gene when he was 61. He was invited to take part in a targeted screening trial involving annual PSA tests, which caught his cancer early and "saved his life".
Again, implementing this would be complicated. Men with a family history of cancer would need to be referred for genetic testing on the NHS by their GP to confirm a BRCA mutation.
The NSC's meeting on Thursday will be chaired by Sir Mike Richards, a former NHS cancer director and chief hospital inspector. The committee's recommendation will be opened to a 12-week consultation, during which time public clamour for prostate screening is likely to continue. Wes Streeting, the health secretary, would be under pressure to overrule the committee if its recommendation falls short of mass screening.
David James said: "Men are calling out to be proactive about their own health. I'm not saying the public's desire for something should be the only thing taken into account, and you ignore science completely, but taxpayers are the people who fund health care. If you have spent your whole life paying into a system, and the system sort of neglects you, how fair does that feel?"
Nick James added: "The case for PSA screening for prostate cancer is getting increasingly strong. Overall, the numbers needed to screen, and numbers needed to treat, to prevent a prostate cancer death are now similar to those seen in established screening programmes for breast and bowel cancer. Logically, given that these programmes exist, screening should now be extended to men for prostate cancer."
He said it was important that the practical difficulties and evidence gaps did not lead to further delay, adding: "We should not however let the perfect be the enemy of the good -- the data are already sufficient."
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Scientists are confident that, whatever the decision next week, it will be a stepping stone towards mass screening for all over-50s.
On Friday, the first of 300,000 men were invited to take part in a £42 million trial called Transform, run by Prostate Cancer UK, which will examine the best ways to run a national screening programme. It will go beyond using notoriously unreliable PSA tests, also looking at other methods such as fast MRI scans and genetic spit tests.
Streeting said: "When the UK National Screening Committee share their initial findings on screening for prostate cancer, I will look carefully at their recommendations as I am determined to bring about genuine change."