Whenever Mr Koh Teck Hoe had to deal with a bout of severe stomach pain, one of the things he turned to was a cigarette.
Even after going for a computed tomography (CT) scan at National University Hospital, the delivery driver continued to puff to take his mind off the pain.
He had also been suffering from a loss of appetite and constipation for several months, which caused him to lose 26kg.
He delayed going for a hospital check-up even after being referred by a general practitioner, afraid that being diagnosed with a serious medical condition would affect his job.
It was in the midst of puffing a cigarette that Mr Koh received a call from the hospital. It was to prepare him for surgery to relieve his bowel obstruction, which was caused by a tumour.
At the hospital, he was diagnosed with stage three colorectal cancer after undergoing surgery, five days after he was admitted.
A heavy smoker since the age of 14, he found out that smoking could have contributed to his cancer. At the peak of his habit, he would smoke 20 sticks daily.
"I decided that I would stop smoking if it would help me recover," said Mr Koh, now 58, recalling the events three years ago.
Dr Tan Ker Kan, a consultant with the division of surgical oncology (colorectal surgery) at the National University Cancer Institute Singapore, advised his patient to quit smoking and exercise more, in addition to undergoing chemotherapy.
After eight cycles of chemotherapy, combined with drastic lifestyle changes, Mr Koh was finally cancer-free, more than a year later.
He now jogs 5km at least once a day in between delivery jobs, and plays badminton during the weekends with his family.
"When I found I didn't have cancer anymore, I realised how precious life is and I treasure it," said Mr Koh, who is married with two children, a 25-year-old daughter and a 21-year-old son.
He has kept his job, and helps out at his older brother's chicken rice stall after work.
Even though "many other colorectal cancer patients do recover well", Dr Tan advises people to go for screening early because it is one of the few cancers where numerous reports have shown that "early screening improves survival outcomes".
It is the top cancer here, with 9,807 people diagnosed between 2011 and 2015, according to the latest Cancer Registry report.
More than half were diagnosed in the late stages (stage three and four), and one in five was below the age of 55. Screening includes a faecal occult blood test, colonoscopy and CT colonography.
Mr Koh continues to go for twice-yearly checks, including blood tests and CT scans, to ensure his cancer remains in remission.
"Doing exercise is very good (because) it's a substitute for taking a lot of medicine," he added.