Two-time world champion Elliot Willis has been diagnosed with bowel cancer.
Willis, 32, was one of the first British athletes to be chosen for next year's Rio Olympics but will take time out from training to have treatment.
Sevenoaks-born Willis teamed up with London 2012 silver medallist Luke Patience in a bid to become Britain's first 470-class Olympic champions.
Willis said: "It's shocking news. It's still my dream to win Olympic gold but my health is my number one concern."
The longer-term impact on his and Patience's 470 campaign for Rio will be determined by how he responds to treatment.
"Elliot needs to do what's best for him," said Patience. "I will support him in whatever way I can."