Alex Finn, 3, became sick during the fall of 2007. He was diagnosed at Johns Hopkins with the form of leukemia that has the highest survival rate.
"They said it was the best case for him," said Jen Finn, Alex's mother.
Alex was released from Johns Hopkins just a few days before Christmas and has been treated as an outpatient ever since, Jen Finn said.
Alex has successfully made it through two phases of treatment and will be going through the third and final phase of treatment for three years, she said.
At the start of Saturday's walk, Alex's white balloon was tied to his hat as he held on to his mother's hand.
Kevin Finn, Alex's father, became involved with The Leukemia & Lymphoma Society in January, shortly after his son was diagnosed. Saturday was the family's first walk.
Their fundraising was "amazingly productive," Jen Finn said. "I was surprised how willing people are to help out."
The money raised goes toward leukemia and lymphoma research and family services, said Suzie Menard, the committee chair for Washington County's Light the Night.
Last year's walk raised about $37,000, and this year they hoped to raise $40,000, she said.
About 200 people were registered for the walk, which was the third annual Light the Night in Washington County, Menard said.
Federal Little League players led the walk, and Hagerstown Outlaws All-Stars cheerleaders cheered on the walkers at the start of the 1.5-mile loop at Fairgrounds Park.
While she has not been affected personally by the diseases, Menard has worked with the society for 10 years, she said.
"It's the one cancer that can hit anyone, anytime," Menard said.
Alex Marinelli's father echoed her sentiments.
"It affects men, women, children, young, old," Paul Marinelli said. "It plays no favorites."