Paralympian David Smith has been forced to give up on his bid to compete at the Rio Games because he needs further surgery on a spinal tumour.
The 37-year-old was hoping to be part of the Great Britain Para-cycling team after winning rowing gold in 2012.
The Scot has already recovered from three rounds of surgery on the tumour, including two in 2010.
"Knowing that everything I've worked for is about to be taken away from me is hard," he said.
"The words didn't even have to leave my surgeon's mouth, I knew in the moment all my dreams for 2016 had gone.
"For me, it's never been about winning medals in cycling, I just wanted to live and love the sport. In this one moment it was taken away from me and no matter how hard I fight there is nothing I can do about it."
Last September, when the tumour returned, he said he wanted to delay surgery in a bid to make it to Rio but he now says that it has grown so much that if it was left alone it would crush his spinal cord and he would stop breathing.
"Letting go of Rio is one thing, and to be so close to the World Championships is hard but the real difficult part is I feel so healthy and love life," he added.
Smith, from Aviemore, won gold as a rower at the London Paralympics in the mixed coxed fours but switched to cycling after the Games.
In June 2015, seven months after his last surgery, he cycled up Mont Ventoux in France three times in one day.