Billy Starr was cold, wet, tired — and inspired.

He’d just finished a grueling 400-mile hike through the northern and most difficult part of the Appalachian trail. Along the way, he’d also spent a lot of time thinking about a very basic principle of life: “To reap the rewards, you have to do the work.”

He’d also spent a lot of time thinking about the end of life. His mother had recently died of malignant melanoma. She was only 49 years old. Starr was only 25 at the time.

Losing his mother to cancer was tough, but Starr was tougher. He sensed that the best way to work through the emotional pain was to take on a daunting physical challenge — and to come out on top, no matter what.

So Starr organized a group of three friends to trek through the toughest part of the Appalachian Trail. It was no stroll in the park for any of them, that’s for sure — they were pelted with freezing rain for the first eight straight days of their trek. The others wanted to abort the hike, but Starr encouraged the group to keep going no matter what, to keep focused on the challenge.

He didn’t just encourage them, either. He led by example — staying focused on the task at hand, refusing to break away from the itinerary he’d so carefully planned in advance, finishing the 400-mile journey as firmly committed to overcoming all the obstacles in their path as he was the day they left Katahdin.

The experience left Starr with a new understanding of what it takes to succeed against all odds. He understood that those who put in the mental energy — not just the physical energy — will ultimately follow their goals from the original theory to the total mission accomplished. From that point forward, Starr knew he could accomplish anything to which he committed his mind as completely as he did his body.

In 1977, Starr initiated a new annual routine. He would wakeup at 4 a.m. and hop on his bike, focused on making it to Provincetown with enough time to catch the 3:30 p.m. ferry back to Boston. The grueling 140-mile ride, accomplished with amazing speed, was something he did for fun. But he didn’t just leave it at that.

In 1980, Starr led dozens of friends who together had decided that they could do more than just achieving speed or testing their endurance by repeating that feat. This time they made an entire weekend out of it, and set a goal of using the ride to raise money to combat cancer, a disease that had claimed Starr’s mother, his uncle, a cousin and the lives of so many others.

At the end of that first weekend, the 36 riders had ridden 220 miles and had raised over $10,000 for the cause along the way. They donated it to the Jimmy Fund, which supports cancer research and care at Boston’s world-renowned Dana-Farber Cancer Institute. Starr had found his calling, and the Pan-Massachusetts Challenge was born. He committed himself to organizing the PMC each year, and told Dana-Farber officials to expect annual checks that would increase in value.

And Starr stayed true to the commitment that day. 28 years later, the PMC has grown considerably and consistently from its modest beginnings into an event that draws nearly 4,800 cyclists, who hail from 36 states and six countries. Since 1980, the PMC has raised more than $171 million that has been used to improve the lives of those suffering with cancer. This year the organization he founded expects to raise $27 million from the efforts put forth by PMC cyclists on August 4 and 5, 2007. It is the largest single contributor to the Jimmy Fund, bringing in nearly 50 percent of its annual revenue.

The nationally-recognized annual Pan-Massachusetts Challenge is a tribute to Starr’s unending desire to achieve, make a difference, and raise money for cancer research. His total commitment to putting his body where his mind’s goals are has made him a powerful role model for others who, like him, know they have to be willing to do the work in order to reap the rewards.

Senator Kerry is one of those others. He’s not alone, either. He’s out there riding the full Pan-Massachusetts Challenge circuit along with the thousands of others who gather each year to raise money for a noble cause while putting forth the grueling effort of riding riding up to 192 miles for charity in one weekend.

Riding in the PMC is a way to channel physical, mental and emotional energy into something much greater than the athletic accomplishment itself. PMC cyclists use their strength to help those who cannot. And with each mile pedaled, the PMC brings researchers closer to finding cures for various types of cancer that affect millions of people each year.

JK knows that it takes more than individual determination to overcome the odds and best the challenge. With him this cause is personal, but it’s also more than that. He knows that it takes teamwork and mutual determination on the part of many people to accomplish a mission as large as the one the PMC takes on every year.

And that’s why he’s asking you to pitch in and help out, too. Here’s how JK put it in the email that he wrote to his online supporters today:

This one isn’t political, but I hope you’ll give me a chance to ask you to join me in something bigger than just politics.

One thing I know is that cancer changes you — whether you have it yourself or know someone who battles it.

I am proud to be a cancer survivor with a clean bill of health since 2003.

Not everyone in my life has been so lucky. The same cancer I had took my father almost seven years ago, and cancer took my former wife-my children’s mother-last year.

It’s for them, and for all of the people who may get the disease, that I ride in the Pan Mass Challenge again this year — I hop on my bike this Saturday. This race raises money for cancer research and treatment. We’ve made great strides in those areas; I’m living proof of that — but those we all know and love who weren’t so lucky remind us we have more miles to go than there are miles in this race.

So, please, go here and support my ride with a pledge of support. Help raise money for this important cause.

The money raised will go to the Jimmy Fund. Anyone who grows up in New England knows all about the Jimmy Fund. As a New Englander, I still remember those photos in the newspaper and those ads between innings — the images of our heroes Ted Williams and Yaz asking each of us to pitch in to help children struggling to beat cancer.

There’s a reason The Jimmy Fund sign is there on The Green Monster in Fenway Park, a fact which will be brought home to all of us in Red Sox Nation when Jon Lester pitches from the Fenway mound for the first time very soon on his own courageous comeback journey.

This is an outstanding charity that has done decades of important work, and last year this race represented a full 50% of the income of the Jimmy Fund. So this is a very important event for a cornerstone organization in our fight against cancer.

Please help me support the Jimmy Fund.

I’ve worn a yellow “Live Strong” bracelet since I was given my first one at a rally in Sioux City, Iowa by a woman I will never forget. It’s a reminder to me of how lucky I am, and how much more work we need to do. I’ll ride on Saturday with thousands of others, leading a team of folks who work in my office, with that woman in Sioux City in mind, as well as all the others affected by cancer.

Thank you,

John Kerry