In 2012, Matthew Piratzky was diagnosed with leukemia. He was 18.

The high school senior from Galloway Township, New Jersey, began chemotherapy on June 14, 2012, and went into remission on October 18, 2012. But he still faced an additional 39 months of chemotherapy to prevent the cancer from returning (his young age increased the risk of recurrence).

During one of his hospital stays, Matthew’s father, Tom, asked his son, “What are we going to do when you’re finished with all this treatment?”

They made a pact to run a half marathon. Tom, 58, had once completed the distance but had since gained weight. “Matt’s big thing was getting me back in shape,” he said.

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Matthew went on to finish his senior year of high school and then start classes at St. Joseph’s University in Philadelphia. “The chemo made me tired, but I wanted to be normal and not remind myself about what I had,” said Matthew, who is now 21. “At times, I wanted to quit treatment.”

Tom said there were many days where he could not fathom what his son was enduring. “From the time he was diagnosed, he has never once complained,” Tom said. “He’s been determined to fight it and never once let the disease stop him. I don’t know how he did it.”

On September 2 this year, Matthew completed his final chemotherapy treatment. Six weeks later, he and his father ran the Atlantic City Half Marathon in Atlantic City, New Jersey, which coincidently fell on the three-year anniversary of his cancer remission.

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Matthew and Tom participated on behalf of the Leukemia & Lymphoma Society and raised more than $6,400 by race day. They ran the first few meters together, and then Matthew took off on his own.

Matthew finished in 2:50:34. “I was tired but happy that it was all over,” he said.

When he spotted his dad approaching the finish line, Matthew hopped back onto the course, grabbed his dad’s hand, and completed the final few meters alongside him. “He was there for me the whole time during my treatments, so at the end, I wanted to be there for him,” Matthew said.

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Tom, who lost about 45 pounds during training, was the final finisher of the race, completing the distance in 4:05:33. “Thank God I had sunglasses on because I was crying,” Tom said. “It was very emotional. All I kept saying to myself during the race was, I just want to finish this for Matt and for every one of those kids that are going through this. I did a lot of praying on the course.”

The duo said they are committed to running another half marathon in the future for the Leukemia & Lymphoma Society. Tom said his son’s prognosis is good and that doctors expect him to live a full, healthy life.

This article originally appeared on RunnersWorld.com.