By Yereth Rosen

ANCHORAGE, Alaska (Reuters) - Lance Mackey won the Iditarod Trail Sled Dog Race on Tuesday, becoming the first musher to notch four consecutive victories in the world's most famous dog-racing event.

Mackey reached the Nome finish line with an official race time of eight days, 23 hours, 59 minutes and 9 seconds, the second-fastest Iditarod time ever recorded in the 1,150-mile race from Anchorage.

"This is for all my fans and the people who believed it could happen," he told a crowd of spectators lined up along Nome's Front Street, where he was greeted by family members, the mayor and other dignitaries.

"To be honest with you, I didn't' know if it was possible or not. With the field of teams, the mushers that are so focused at the moment, on beating me," he said, after hugging his wife, handing her a bottle of champagne he had tucked into his sled and hugging his dogs.

"Midway through the race, I didn't know if I was going to be able to pull it off."

No other musher -- not even Susan Butcher or Rick Swenson, who dominated the Iditarod in the 1980s -- has ever notched four consecutive wins.

For Mackey, this year's championship also provided some personal vindication. A throat-cancer survivor who has a prescription for medical marijuana, Mackey believes he was the target of a new Iditarod rule requiring mushers to submit to drug testing.

Mackey admits he regularly smoked marijuana on the Iditarod trail in past years, a practice he said helped with pain management and appetite enhancement. His cancer treatments left him without saliva glands or taste buds.

He declared he would not use marijuana during this race, even though he had a prescription to do so.

For his victory, Mackey will take home a cash prize of a little over $50,000 and a new truck.

The son and brother of past Iditarod champions, Mackey has a reputation for toughness. When his left index finger became compromised by nerve damage sustained during cancer treatment, he chopped it off himself. In 2007, he became the first person to win the 1,000-mile Yukon Quest International sled dog race and the Iditarod back to back, a feat he repeated in 2008.

He is also known as a canny racer, who sometimes skips or shortens rest stops at race checkpoints to keep his rivals off guard, or sneaks out when other mushers are sleeping or otherwise occupied.

Earlier in the race, four-time champion Jeff King appeared poised to claim victory. But Mackey passed him Saturday as the leaders were racing down the frozen Yukon River.

As of Tuesday afternoon, King was in third place, still heading along the Bering Sea coast to Nome.

In second place, about an hour and a half behind Mackey, was Hans Gatt, an Austrian-born musher who lives in Whitehorse, Yukon. This is Gatt's best finish in the Iditarod; last month he won the Yukon Quest in record time.

Seventy-one mushers started the race on March 6 with a ceremonial, untimed 11-mile run in Anchorage. As of Tuesday afternoon, while Mackey basked in his victory, 56 were still on the trail to Nome and 14 had dropped out.

As has been the case with other sports events, the Iditarod has been pinched by hard economic times. Corporate sponsors have pared back support, a trend reflected in the prizes offered to mushers.

This year's total prize purse is about $590,000, significantly less than the $925,000 paid out two years ago.

(Editing by Todd Eastham)