But the Christchurch 57-year-old didn't believe them and her daughter and niece scoured the internet for a miracle. They found one.
After sending more than 30 emails to clinics around the world, they were contacted by a professor at Harvard University and Ms McKay was invited to take part in a drug trial in Boston.
It was while living there for two months last year that she heard her pride and joy, Franco Nelson, run a close second in the New Zealand Cup, one of the world's biggest harness races.
"I was actually undergoing treatment when the race was on and for a lot of the time I was violently ill," she says. "But I watched a replay two hours after and it was amazing. It meant so much to me."
Not long after, Franco Nelson, a 6-year-old stallion, started to struggle with physical problems that have seen him unable to race since January 9.
For a horse to contest the 3200m race today without a lead-up race in nine months is almost unheard of. The last horse to do so successfully was Wildwood Junior in 1910.
But after Franco Nelson performed well in a workout last week, Ms McKay, who owns him with her parents, decided to approve the radical pathway to the race.
"I wanted to give him his chance to prove everybody wrong, like I got my chance," she said. "He had had his problems, like me, but he is sound and healthy so we want him to start.
"One thing I have learnt is you have got to live life when you have the chance."
Ms McKay flew back to Christchurch last night from Melbourne, where her treatment continues.
"The cancer has stabilised and while there are side effects, at one stage I had 13 lesions on my liver, now they can find only four.
"It has been a hell of a battle, and had this happened 20 years ago, when you didn't have access to the internet and been able to contact the people we were able to, well, I wouldn't be here."
Franco Nelson contests the New Zealand Cup at Addington at 5.15 tonight.
