BG Lee kept his parents posted daily on developments. Was there any sign that the cancer had spread to other parts of his body besides the rectum?
The weight on their minds was lifted when the doctors found that there was none.
They were anxious that treatment be started immediately but the doctors advised that it was better to get confirmation of the diagnosis and an agreement on the treatment first.
After discussing it with his doctors, BG Lee decided to go to Stanford University Medical Centre in San Francisco. The medical results would also be sent to the University of Texas' M D Anderson Cancer Centre in Houston.
Meanwhile, the Lees phoned their daughter, Wei Ling, 38, who was then studying epilepsy in the Toronto Sick Children's Hospital in Canada. When told of BG Lee's plans, she advised him to go on to Houston after San Francisco.
Dr Lee, who had spent three years in Massachusetts General Hospital doing paediatric neurology, knew that unless the patient was there at the medical centre, American doctors would not give a full opinion on the patient.
It was advice that SM Lee would later acknowledge as particularly useful, as the Houston recommendation, in his mind, made a difference to the treatment.
Before BG Lee and his wife made their trip, SM Lee called his younger son, Hsien Yang, to help the maternal grandmother take care of the couple's daughter and three sons when their parents were away.
While worrying about their son's health, the Lees continued with their trip, visiting a game reserve, moving on to Cape Town, spending time with Afrikaan farmers on the plains in Karoo, and then flying on to Mauritius.
Every day, late at night or early in the morning, SM Lee would ring Singapore, making allowance for the six-hour time difference. The exception was at the game reserve, where there was no easily accessible telephone line.
It was not without some strain on them. "You are carrying a nagging burden and a psychological load. So you don't enjoy your food so much, you don't take in the sights as an ordinary tourist. But you go through with the programme. That's life."
But to those who were not in the know, the Lees appeared much as usual.
Straits Times journalist Zuraidah Ibrahim, who was covering the trip, said that there was not the slightest hint that the Lees were in any way troubled. She recounted how the Senior Minister had exchanged pleasantries with reporters while they were boarding the bus for the airport to fly to Cape Town. "He even asked us if we got mugged," she added.
Next: Work goes on.