The Iditarod Trail Committee announced Monday that former champion Lance Mackey has withdrawn from the race, citing health reasons.
The committee shared the news through its Facebookpage, writing Mackey is on a "journey to improving his health."
Mackey is a cancer survivor, and has had difficult time in the last two Iditarods, scratching in 2016 midway through the race.
The musher's four back-to-back wins in both the Iditarod and Yukon-Quest make him one of the most elite long-distance mushers in the sport's history.
Calls to Mackey's Comeback Kennel in Fairbanks went unanswered Monday afternoon.
There are currently 54 mushers signed up for the 2017 Iditarod.