By DARRELL HALEN

Three years ago, when he was only 15 months old, Declan Rourke of Bedford had a tumor surgically removed from his brain. Now, his family is raising money to help other young patients struck by the same disease.

Declan’s family is part of a team that will participate in the Boston Marathon Jimmy Fund Walk on Sunday, Sept. 13, to support cancer treatment at the Dana-Farber Cancer Institute in Boston.

There are five routes – ranging from 3 miles to 26.2 miles – available to participants.

Organizers of the annual event expect that this year 8,000 walkers will raise $6 million through small and large donations.

“I think that’s one of the great advantages of the walk – that everyone can participate,” said Declan’s mother, Mel Pepin. “You just have to choose what level.”

Declan was diagnosed with an atypical teratoid rhabdoid tumor on Father’s Day 2006. The ping-pong ball size tumor was removed at Dartmouth-Hitchcock Medical Center in Lebanon two days later, and he went through cancer treatment at Children’s Hospital Boston and the Dana-Farber Jimmy Fund Clinic.

“The best treatment in the world was in our back yard,” said Pepin, whose son lived in a hospital for six months. “We could not have been any luckier in that sense. People travel great distances to go to Dana-Farber.”

AT/RT strikes children usually under the age of 3. The tumor can be found anywhere in the brain and tends to spread through the central nervous system. Because it is highly malignant, AT/RT carries a high mortality rate.

Declan appeared to have a stomach bug when he first showed signs of being sick. After he vomited in his crib, his parents discovered he was not moving on his left side and his lips were starting to twitch.

“We were lucky he had a major episode that told us something was wrong,” said his father, Tym Roarke. “Often times, that doesn’t happen. Because of the fact we caught it so early is one of the reasons why he is doing so well.”

Today, Declan, who finished chemotherapy treatment in October 2007, has no evidence of the disease. There are, however, after-effects from his treatment, which also included radiation.

Declan has significant hearing loss, takes medication to control seizures and wears leg braces. He may show cognitive delays in his middle school and high school years. Damage to his heart and other organs may be discovered as he gets older.

“It’s a guessing game whether or not – and to what extent – he’ll manifest those (problems),” said Roarke, whose son could experience a secondary cancer as a result of chemotherapy drugs. “You just don’t know until you’re there. His doctors and people compliment how remarkable he looks and how remarkable he’s doing right now, compared to how incredibly sick he was. But (there are) other things that can crop up much later on.”

When Declan’s tumor was discovered, only one option for treatment, known as IRS III protocol, showed any promise. If they didn’t pursue it, the Rourkes would lose their son.

“When you’re (faced) with … you have no option but you can try this protocol that could potentially save his life, it’s kind of a logical choice,” said Pepin.

Family, friends, co-workers and even strangers rallied to support Declan and his family after he was diagnosed.

They received hundreds of greeting cards which they placed on the walls of their dining room.

“We needed that,” said Pepin. “That was our visual reminder of how many people were supporting us.”

And a fundraiser at the Manchester Country Club in September 2007 helped pay for some important expenses, including Pepin’s $1,500 a month COBRA insurance that would enable the family to cover the $1.6 million cost of Declan’s treatments.

In the United States, only around 30 new AT/RT cases are diagnosed each year. Because of the small number, it’s difficult for doctors to definitively conclude which portions of treatment actually work on patients.

Five families affected by AT/RT, including the Pepin- Rourke family, are teaming up to support the “Cure AT/RT Now” Fund at Dana-Farber by participating in the September walk. Their team, which has 64 members, has set out to raise $30,000.

The fund supports the work of the Jimmy Fund Clinic’s Stop and Shop Pediatric Brain Tumor Program and the work of two doctors, Susan Chi and Mark Kieran.

According to the team, Jimmy Fund Clinic researchers and clinicians are improving knowledge and treatment of AT/RT through cutting-edge research and by consulting with experts world-wide. Since the first Jimmy Fund walk was held 20 years ago, $60 million has been raised to support cancer treatment at Dana-Farber.

On the personal page she created at jimmyfundwalk.com, Pepin suggests donations that match experiences Declan has gone through.

For example, a dollar given for every round of chemotherapy that Declan has received would raise $57, and a dollar donated for each of the approximate number of nights he spent in the hospital would bring in $267.

Pepin is planning to walk the fundraiser’s 13.1-mile route and will be joined by her husband and son for the last five miles. Her father, Joe Pepin, a Bedford resident, is walking 26.2 miles.

The family invites the community to help them in three ways: walking with them, making a donation or sharing their story. They want to help provide better treatment – and hopefully one day a cure – to the patients of pediatric brain tumors.

“We’re very open about Declan’s experience,” said Pepin, whose son undergoes periodic tests to monitor his health and development. “Sharing our story helps us, it helps Declan and it helps raise money to make things better for other kids.”