On Aug. 3 and 4, 12 Darien cyclists will participate in the 34th annual Pan-Mass Challenge, an annual bike-a-thon that has raised $375 million for adult and pediatric cancer care and research at Dana-Farber Cancer Institute through the Jimmy Fund.

Cyclists and PMC volunteers will travel from 36 states and eight countries to ride in the PMC this year and more than 350 riders are cancer survivors or current patients.

"The PMC is the most successful athletic fundraising event in the country, it raises and contributes more to charity than any other," Jackie Herskovitz, a PMC spokesman, said. "We give 100 percent of every rider-raised dollar directly to the cancer research and treatment center at Dana-Farber."

Billy Starr founded the PMC in 1980 after he lost his mother, uncle and cousin to cancer. The ride runs through 46 towns across Massachusetts, and approximately 5,500 riders will participate this year.

"Being a part of America's largest single charitable fundraising event is a big thrill," Darien cyclist Graham Hill said.

Hill has wanted to bike in the event for the past three years, after meeting Billy Starr on a ski trip, but couldn't until this year when he moved from England to the U.S.

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"An organization such as Dana Farber, renowned for fighting cancer, is something I want to support, especially as friends and family continue to be affected by the disease," Hill said.

"For a couple of days you find yourself in a positive oasis of goodwill," Darien cyclist Terry Bock said.

Bock is participating in his seventh PMC. Prior to competing in the challenge, Bock said he wasn't much of a biker, "not unless you consider riding your bike around as a middle school kid." However, seven years ago he was inspired to ride in the competition as what he called a "kind of athletic mountain to climb" after being off of his feet for several years due to a personal injury. "I found myself very, very interested not only in continuing to do it (the PMC), but also inspired by the cause."

The PMC has made an effort to accommodate a vast range of bikers with 11 routes of varying distances designed to cater to all levels of cycling strength and fundraising ability. Cyclists from Darien will participate in either one- or two-day rides this year.

"I will ride the longest and hardest of the one-day routes," Darien rider Marcelo Castro said of his 111-mile ride from Sturbridge, Mass., to Bourne, located on Cape Cod.

"The key is to build endurance," Castro, who is participating for the first time, said of training for the PMC. "The basic training is to do long rides, starting at 30 miles or so and building to around 80 miles two or three weeks before the ride."

A number of different factors inspired Castro to participate in the fundraising event.

"The PMC truly makes a difference and it is great to be part of something bigger than oneself," he said. "On a more personal level, my inspirations are my mother-in-law, who recently lost the battle to pancreatic cancer, and my son, Pablo, who has joined me in many long rides."

The Darien riders are looking forward to the camaraderie that comes with participating in the event and supporting the Dana Farber Institute.

"The energy that people share with each other and the feel-good vibes ... you just don't experience that in your everyday life," Herskovitz said.

To support riders and the Dana Farber Institute, log on to: www.pmc.org and click the "Donation" button.

Mac McDonough is a freelance writer.