William Dunnachie, 69, was admitted to Forth Valley Hospital in Larbert, near Falkirk, with suspected food poisoning in 2017 from a takeaway steak pie supper.
Surgeons had to perform emergency surgery on Mr Dunnachie's gallbladder and noticed abnormalities in his kidney.
Subsequently, he had to have his gallbladder and kidney removed at the Queen Elizabeth University Hospital in Glasgow.
The pensioner was offered the opportunity to join the Keynote-564 drug trial which was designed to prevent the recurrence of kidney cancer.
Mr Dunnachie was monitored closely and now, almost five years later, the retired labourer remains cancer-free.
The drug used in the trial, pembrolizumab, a specially designed immune-stimulating drug which helps minimise the chances of kidney cancer recurring, has been approved for use by the Scottish Medicines Consortium.
The trial was led by Dr Balaji Venugopal, consultant in medical oncology at the Beatson West of Scotland Cancer Centre in Glasgow.
"I just feel extremely lucky. If I hadn't bought that steak pie, I might not be here today," Mr Dunnachie said.
"You could say it helped save my life. But the team at The Beatson have been fantastic throughout my experience, and I was delighted to be able to give something back by participating in the trial. Now it's been approved, it's humbling to know it will help potentially thousands of people in the future."
Dr Venugopal said: "Many patients who have a cancerous kidney removed at surgery will be cured, but, in some, the cancer will recur, and it may spread to other parts of the body.
"The kaynote trial has shown that patients who receive an immune-stimulating drug called pembrolizumab for a year after surgery have a significantly lower risk of recurrence.
"This is the first time an immune-stimulating drug has been shown to do this. A team of dedicated patients and staff at the Beatson took part in this trial, which was conducted all over the world, and the results of the trial are promising for our patients.
"It is exciting to note that Scottish Medicines Consortium has now approved pembrolizumab to be available to all patients in this situation in NHS Scotland."