Jon Paul McAllister, 38, and his partner Craig Park went on holiday to South Africa, Madagascar and the Seychelles to celebrate the end of Mr McAllister’s chemotherapy treatment and their January engagement.
Mr Park said a scan showed the treatment was shrinking the deposits left behind following surgery to remove a tumour and the couple were advised they were fine to go on the long-awaited trip.
In Madagascar, Mr McAllister’s health deteriorated rapidly and, having been transferred to improved medical facilities on nearby island Reunion, he is too sick to return home on a commercial flight.
Friends started a fundraising campaign on Friday to pay for the overseas treatment and an air ambulance flight back to Scotland, which they said the couple’s insurance will not pay out for.
The money raised is now more than a third of the way towards the £35,000 target.
Mr Park told the Press Association: “We are speechless. People’s kindness and generosity is amazing. We weren’t expecting this at all.
“Jon Paul has spent his working life giving to other people. He constantly looks after all his clients, friends and family and is extremely selfless.
“He never asks for anything but this is one of those times where he needs help.
“Being 38 he never expected the news we received about his stage four cancer and after chemo he thought everything was ok.
“It’s really taken its toll on him, and at this moment in time needs to be home, surrounded by loved ones and receiving the medical attention he deserves and needs.
“He is still constantly vomiting and unable to keep down fluids or food.
“The only thing keeping him alive is the drips he is on as he has no other way to get the proper nutrients and energy he needs.
“He hasn’t drank or eaten food in over two weeks.”
Mr Park said translation problems mean they are struggling to understand exactly what is wrong with his fiance, with medics indicating scans suggest it could be another tumour.
He added that before leaving home in Rutherglen, South Lanarkshire, social worker Mr McAllister had not received his final scan results.
He said: “His half way scan showed chemo was working and the ‘deposits’ left behind after his tumour was removed were shrinking.
“We asked so many times if this holiday was ok and we were told just to go ahead with it, there was no reason we shouldn’t go on holiday.”
Karen Bell, who set up the fundraising page, urged people to help the couple return home.
She said: “We’re desperate to get Jon Paul home to receive the best treatment possible.”