ANCHORAGE, Alaska (AP) — Organizers of the Iditarod Trail Sled Dog Race say four-time champion and cancer survivor Lance Mackey has dropped out of next year's nearly 1,000-mile race because of health reasons.

Race marshal Mark Nordman confirmed the withdrawal to The Associated Press on Monday after the Iditarod Trail Committee announced it on its Facebook page.

Mackey could not immediately be reached for comment. He started last year's race, but later scratched because of health concerns.

Mackey was diagnosed with throat cancer in 2001 and underwent extensive surgery as well as radiation treatment and the loss of his salivary glands. After returning to the sport he went on to become the only musher ever to win both the Iditarod and the 1,000-mile Yukon Quest International Sled Dog Race in the same year. It's a feat he has accomplished twice.