Greg Maciulla, on hormone therapy for prostate cancer, plans to ride 104 miles in less than five hours.

How do you define a life?

Not by cancer, it sure sounds.

No, Greg Maciulla’s life is defined by his friends, his family and, in a big way, Tucson Medical Center El Tour de Tucson.

He’ll give it the old college try one more time this year — if that college is Yale or Harvard or Oxford. Greg isn’t settling for a simple joy ride throughout Tucson, his home. He’s seen it, often by two wheels, often early in the morning, for going on 32 years.

No, he and a team of family, friends and supporters are gunning for a platinum time on Saturday, taming the 104-mile race in five hours or less. He’s been doing it for years, why change now?

“I’ve also been a person who sets goals and tries to meet them,” Maciulla said. “I’m not a fanatic about it. This year, the El Tour event might be an example of hope springing eternal. But that’s OK.”

OK, but why?

The question has been posed multiple times, in a myriad of ways, but the answer just doesn’t seem to come. Not right now, at least. Maybe there’s no answer.

We understand the what, the when and the where — Maciulla will attempt a platinum time at El Tour — and the how: he’ll have the Big G Racing team of more than 20 riders, most half his age riding along with him and pushing him forward.

But we still do not understand the why.

If Maciulla, who is 69 years old and on hormone therapy for prostate cancer with a TKO of colon cancer already under his belt, decided to take it easy this year and stayed home, you’d understand. If he tried the shortest race, enough to build up a good sweat, OK, fair enough. If he simply attempted the big race with no time limit, taking in the crisp Tucson air, sure, we get it.

So why even set this goal, this blistering pace?

“I guess you’d have to refer the question to a psychiatrist,” Maciulla said. “Or my priest, I don’t know. It’s just the way I’ve always done things. I give it my best shot, I get involved.”

It’s what made him even get involved in cycling in the first place.

He’d poured much of his life into his career as an obstetrician/gynecologist at Tucson Medical Center, and he needed an outlet. It was 1983, and he was, as he calls it, “a fat physician.” He bought a bike, and “aged it for a year in the garage,” Maciulla said. It just sat there. Finally he put it to use.

His first El Tour was the “hardest thing I’ve ever done,” and took over eight hours to finish. Training begat training, though, and soon he was a dyed-in-the-wool cyclist. Soon it was a family thing; In 1992, El Tour dedicated the race to Team Maciulla of Greg along with his first wife, Trudy – who passed away in 1993 – and kids, John, James and Julie. He’s done El Tour nearly 30 times, finishing as high as 15th in 1993, and he’s ridden for Team Colleen, another fundraising cycling team, multiple times. He and John ride three or four times a week, and he’s continued the family tradition with second wife, Jill, and stepson Mike Rice cheering him on.

One day, though, Greg had enough of Mike’s cheering and pulled him aside for a talk. Mike was overweight, like Greg had once been, and Greg got him on a bike. That next El Tour, Mike stood at the finish line and said, “This is my last time on the sidelines.”

Mike and John helped form the Big G racing team to help Greg try to complete this year’s El Tour in platinum time; Mike and his wife designed the team’s kits.

“He’s infectious: ‘the why’ is that,” said Mike, who has lost 70 pounds since he became cycling. “He’s just passionate for life, and that’s on and off the bike. He never stops. The passion he has for the bike, it’s infection, and he loves it so much, it comes through in everything he does.”

Added John: “It started just to get into shape, but it’s morphed into bonding time. It’s not that we’re talking the whole time, but man it’s something I get to do with my dad. We’ve solved world issues time and time again. Every time this time of year, it’s what we talk about. This is five elections, now.”

Their riding persisted even through Maciulla’s cancer.

He was diagnosed with Stage 3A colon cancer in 2006, requiring surgery and chemotherapy. Shortly after, the prostate cancer diagnosis came in, necessitating more surgery and two rounds of radiation. The two diseases were unrelated, and while the colon cancer went into remission, the prostate cancer has been an ongoing issue, as he currently needs hormone therapy to replace lost testosterone. In 2007, he dropped down to the 25-mile ride, but went right back up to the big race soon after.

Maciulla credits his cycling with aiding in his fight against cancer, though he bristles when called a survivor, as that implies that he has done something different than the others who’ve lost the battle.

He is a doctor, though, so he does dispense some good advice.

“The secret to life is to stay involved and stay in relationships,” Maciulla said. “Cycling really is a team sport. Most people don’t realize that. It really forms relationships. When you’re riding with people, you get to know what people are made of.”

What defines them, even.