TORONTO -- Forty years ago today, on a stretch of road near Thunder Bay, Ont., Terry Fox felt an intense pain in his chest.

He’d already run almost 42 kilometres every day for more than four months in his ambitious cross-country mission to raise money for cancer research. But by kilometre 5,373, the cancer he’d been fighting spread to his lungs, and he was forced to stop running.

Sept. 1, 1980 marked the last day of the Marathon of Hope. Fox died in hospital the following summer at the age of 22.

His older brother, Fred Fox, said that, for him, today is a day for reflection.

“It was people lined up along the road that kept him going,” Fred told CTV News Channel on Tuesday from Maple Ridge, B.C. “But he realized that he had to get to the hospital.”

While today marks the anniversary of a sad ending, Fred said it also represents a hopeful new beginning: the moment Terry passed the torch to his fellow Canadians to continue the mission he started.

“Here we are 40 years later, and Terry’s sacrifice, what he did in trying to make a difference and raising funds for cancer research, has impacted the lives of so many people,” he said.

After Terry was diagnosed with bone cancer at the age of 18, he had his right leg amputated above the knee. The idea to run across Canada for cancer research came to him while he was recovering in hospital.

Fred recalled the moment Terry told the family that he planned to run across Canada. Terry had recently run a race in Prince George, B.C., where he was the only amputee. He finished last and returned home to break the news to his mother.

“Mum was upset, protective mum,” Fred said. “(She) told him he was crazy, said ‘Why don’t you just run through B.C. to raise money that way.’ And Terry said, ‘Mum, not only people in B.C. get cancer, but people right across Canada.’”

After that, the whole family got on board and supported Terry throughout his journey, even joining him for various segments of the run.

Terry’s original goal was to raise $1 for every Canadian — $24.17 million — which was achieved just four months before his death. Since then, more than $800 million has been raised to support cancer research in Terry’s name.

Fred said his brother would never have believed that, 40 years later, his legacy has left an indelible mark on Canada.

“Terry only hoped that his example of never giving up and the example of caring for other people would be carried by other people,” he said.

“He would be so proud that maybe his inspiration, what he did, has inspired so many to continue what he started.”

On Sept. 20, a virtual Terry Fox run will be held across Canada. Participants are invited to collect pledges and then embark on their own non-competitive run or walk in their community. Nearly 10,000 runners have already raised almost $1 million for this year’s event.

Prime Minister Justin Trudeau issued a statement Tuesday calling Fox “a Canadian hero who taught us invaluable lessons about the importance of helping others.”

"His extraordinary accomplishments captivated the country, instilled hope in Canadians, and helped shift their views of people with disabilities. Forty years later, people across Canada and around the world continue to be inspired by Terry’s tenacity and enthusiastic message of hope, which is as timely as ever during the COVID-19 pandemic,” Trudeau said.