Despite flying to the Children's Hospital of Philadelphia for specialist treatment, he tragically passed away in 2014, aged only five. Now his parents, Stephen and Leona, want to help ensure that no family has to suffer in the same way.
Leona said: "What we want to do is fund research which will then hopefully develop into a clinical trial.
"We see families raising hundreds of thousands of pounds when their child is sick, and the focus shouldn't be on fundraising at that point - it should be on the child.
"So if we can do anything to bring that back towards home, that's what we want to do."
Stephen added: "Families shouldn't have to raise half a million pounds to go to America for treatment - it should be here."
The family were joined at Fortwilliam Golf Club by two-weight world champion boxer Carl Frampton, alongside Olympic fighters Paddy Barnes and Michael Conlan.
Carl, who met Oscar on a number of occasions, said that he was inspired by his parents' resilience. "I don't know how they can deal with it," he added. "You need to be such a strong person to get through that.
"It's always heartbreaking to see a kid who is sick. Hopefully, one day before I'm off this planet, there's a cure for cancer and kids can be treated for it."
Carl also told how he had fond memories of Oscar and could to this day remember the little boy's warm smile.
"You think sometimes you have it tough, then you see this kid with a big smile on his face who has it a lot tougher than anyone else I know - it's an inspiration," he explained.
The day cost £180 for each team of four and featured 18 holes of golf, a free burger and beer, prizes, an auction and an evening meal.
Despite the unfortunate weather, dozens of golfers took to the fairways in high spirits.
Fortwilliam Golf Club was chosen because of the Knox family's local roots and their connections to the club.
"When Oscar was sick, I loved to get out here and play some golf," said Stephen. "It was almost like therapy to get out and hit the ball."
Leona also recalled buying her son - "who wanted to copy his daddy" - a half set of clubs for a day out playing at Cushendall Golf Club.
Both praised the support that Fortwilliam and Carl Frampton had given to them.
Stephen said: "He's a brilliant guy. Some people when they get to that level are in their own world, but he's totally down to earth."