Shaluinn Fullove’s world was turned upside down in the early spring of 2005, and to this day, she can’t explain why.

She has a very good question, though: How does a young, active, athletic person who puts in lots of mileage per week as a distance runner end up with cancer?

“Of course, I was surprised,” Fullove said. “I’m healthy, never had a bad check-up in my life. It was really out of the blue that I found this out.”

Doctors told Fullove — who ran cross country and track from 1996 to 2000 at Stanford University — that she had thyroid cancer.

“I had some other symptoms that I thought were related to something else, and it turns out it was cancer,” she said.

Fortunately for Fullove, the cancer was discovered early enough so that she had a good prognosis. She underwent a full thyroidectomy in July and had radiation treatment and was in recovery throughout the fall and winter.

She wasn’t able to do any serious training, but did some relay/team runs with the Google team (JP Morgan Corporate Challenge and Hood to Coast) and some local road races on the Pacific Association of U.S. Track and Field circuit for fun.

“I got it young — I got it over with,” said Fullove. “I really just tried to take it in stride, take care of it, and turn it into a positive.

“My doctor told me to take it easy, especially during my radiation. When he found out I was running, I think he was speechless.”

Fullove started training after her wedding in May 2006 and in October of that year ran her “re-debut” marathon in Chicago, completing the race in a time of 2 hours, 51 minutes, 6 seconds.

She’s done only two marathons — her first was “kind of a whim, without really training too specifically for it,” when she ran a 2:58 at the San Diego Rock ’n’ Roll Marathon in 2003 — but now has her sights set on qualifying for the 2008 U.S. Olympic Women’s Marathon Trials.

Fullove is entered in the 30th annual Kaiser Permanente Napa Valley Marathon, a 26.2-mile race which follows a point-to-point course on March 2 starting at 7 a.m. from Rosedale Road and the Silverado Trail in Calistoga and finishing at Vintage High School in Napa. The majority of the race is conducted on the Silverado Trail.

Known as the “Biggest Little Marathon in the West,” the race has earned a reputation for outstanding runner support, attention to detail, and a beautiful course. Runners — 60 percent of whom are from Northern California — are treated to panoramic views of the valley.

There are a few rolling hills early in the race, but for the most part it’s considered a flat, fast course for what is expected to be a sold-out field of 2,300 runners. It’s a USA Track & Field-certified course.

This year’s race has again been selected by the Road Runners Club of America as its National Marathon Championships. In 1996 the race served as the RRCA California Marathon Championships and in 1997 as the Western Regional Championships; and from 1998-2007 it was the RRCA National Marathon Championships.

Fullove is chasing the Olympic Trials “B” standard, a sub-2:47. The “A” standard is a sub-2:39. The qualifying period began Jan. 1, 2006 and ends on March 23. So Napa is one of the “last chance” qualifying opportunities for women.

This is Fullove’s third try at going for a Trials mark. She’s made it her goal to hit the standard.

“I’ve been unlucky up to this point in a couple of marathon attempts,” she said. “I signed up to run Chicago and was injured and most recently ran in Phoenix. I just was sick and I actually wasn’t able to finish it. I collapsed at Mile 20.

“I’m coming to Napa because I’ve heard so many great things about it.”

Fullove’s coach, Tom McGlynn, the president of Focus-N-Fly, qualified for the U.S. Men’s Olympic Trials here last year with his second-place time of 2:21:24. McGlynn also qualified for the trials in both 2000 and 2004.

Fullove — a Palo Alto resident who works as a product marketing manager for Google, Inc. — is among several elite-level women, including Claudia Becque of Chicago, who will be using Napa to try and advance to the Trials. They’re scheduled for April 20 in Boston, the day before the regular Boston Marathon.

Fullove and Becque will be paced by Caroline Annis, a San Francisco runner who has already secured a qualifying time. Annis was the second American female finisher and the 13th female overall at the Boston Marathon in 2005. Becque and Annis also work with McGlynn. Annis has qualified to date with her 2:45:25 at the Cal International Marathon in Sacramento in December.

“We’ve got a great group of women who are going to go out there and all are going for a common goal,” said Fullove, who majored in American Studies with an emphasis in public policy at Stanford. “Even though it’s my third try, this is probably what it’s meant to be. I’m looking forward to it.

“It’s kind of a last-chance race for a lot of women going for the Olympic standard. Hopefully there’s going to be more women out there. We can have a lot of teamwork going on and we can get that common goal that we’re striving for.”

A knee injury knocked Fullove, 30, out of last year’s Chicago Marathon. In January she said she was having some complications with her thyroid levels.

“I’ve just been kind of staying the course and trying to still go after that goal,” she said. “I’ve had really great medical care. I’ve been fortunate that I’ve had almost no side affects. I’m feeling really good now. I’m feeling really good about Napa.

“I’m just very thankful that I’m able to run at this level and have a real viable shot at it.”

Fullove, a member of the Impala Racing Team, said achieving a Trials mark would be special.

“The marathon is a long way to run fast. There are many other marathons. I could have taken a break and I could go run Boston the day after the Trials. But there’s something special about stepping to the line on that day and vying for those spots. The thing with marathons, it’s any given Sunday, right?

“Just to let yourself unwind with those great women is special. The qualifying is a big goal of mine. It’s going to be a hard goal to get, and I hope I get it. But I know when I’m out there I’m going to execute my plan to run the best race I can that day, so that no matter what happens I can walk off that course and know that I did a good job and be happy with that.”

Fullove said she’s confident with in her training and preparation coming in Napa. She also has a time of 1:20:02 at the San Francisco Half Marathon last year and races in local Pacific Association/USATF road circuit events.

“As much as you thought you knew about running in college, over the last 10 years I’ve definitely learned a lot more about my strengths and my weaknesses and how to stay relaxed under tense situations,” said Fullove, who went to high school at Louisville of Woodland Hills, Calif. “Keeping your cool is a big part. I have felt extremely confident the last two times I’ve prepared to go to the line for the marathon, so I’m hoping the third time is a charm and that I can just go out there and execute.

“I’ve had some time to really focus on my training. I know my body. I know its limits. I know how to push those limits. I think it really does come down to timing.”