DENVER — With no basketball to coach, George Karl is tending to his other passion in life: fighting cancer, a disease he’s beaten twice.

The Denver Nuggets coach lent his voice Tuesday to the American Cancer Society and Quest Diagnostics, which are teaming up on a nationwide cancer prevention study. It aims to follow 300,000 people for 20 to 30 years to see how genetics, lifestyle and the environment affect cancer risk.

“There are a lot of people who want to get into this fight who don’t have cancer, and this is one way,” Karl said.

Karl is 21 months removed from a brutal battle with neck cancer, which came a few years after he beat prostate cancer. His son, Coby, is a survivor of lymph node cancer.

Karl said he’s spending his spare time during the NBA labor impasse speaking at cancer charities and encouraging people to join the fight against the disease.

Karl missed the end of the 2009-10 season because of his illness, then returned last year and guided the Nuggets through the Carmelo Anthony minefield while also recording his 1,000th win, joining Larry Brown, Don Nelson, Lenny Wilkens, Pat Riley, Jerry Sloan and Phil Jackson as members of the NBA’s most exclusive coaching club.

He’s looking much stronger and leaner than he was last season, and his voice is much stronger, which makes it easier for him to talk about preventing cancer.

“I’m very passionate about it. I enjoy talking about cancer,” Karl said. “I enjoy talking basketball more, I’d like to be able to talk basketball but I can’t right now. But you know, my family, everybody has been touched somewhere along the way.”

The NBA locked out its players and canceled the first month of the season. The sides are meeting again this week with the remainder of the season hanging in the balance. Several Nuggets decided to play overseas during this season.

Karl finds himself stumped without a team to teach.

“I don’t know if the word’s difficult. To me it’s just strange. I don’t know what to do,” he said. “I go to work almost every day when I’m in Denver and then about 11 o’clock, I’m going, ‘What the hell am I doing here?’ We’re not allowed to do anything. We’re ready. We’re ready for the season. We’ve just got to wait and see where it goes.”

Without hoops, Karl is continuing his fight against cancer even though he’s been cured.

“I’m in a stage of survivorship, so basically my treatment is to try to be healthy,” he said. “So much of what I’m trying to do is nutrition-oriented, environment-oriented. I’m a big believer that genetics is the field where I think discoveries are going to be made in the very near future, stem cells. I think we are on the verge of successfully making major hits on the battle against cancer.”