More than 14 per cent of Hong Kong people aged 50 to 70 may have bowel cancer or its precursor without knowing it, according to a Chinese University screening programme.
The programme tested almost 11,000 people without symptoms and one-seventh were found to have the cancer - the most common in Hong Kong - or precancerous growths called polyps, higher than in most Asian regions.
The results were revealed yesterday, a few days after Chief Executive Leung Chun-ying announced a subsidised screening programme for the disease in his policy address.
The researchers said global experience was that early detection by the two screening methods used in the tests could reduce the number of deaths by 33 per cent to 68 per cent, as it could take up to 10 years for polyps to progress into cancer.
The results showed the prevalence of the disease is split almost equally between men and women - in contrast to the international trend for more men than women to be affected. But the researchers said this might be because more women than men volunteered for the programme.
"God is unfair - men have a higher risk of having bowel cancer," Professor Justin Wu Che-yuen, director of the university's Institute of Integrative Medicine, said. "But we can't blame it all on God because men are usually less concerned about their health, as we can see from this programme."
Bowel cancer has overtaken lung cancer as the most common variant of the disease in Hong Kong, with 4,450 new cases and 1,900 deaths in 2011, but it still remains the second biggest killer behind lung cancer.
In the tests on 10,732 people between 2008 and 2012, 1,512 people were found with the cancer or precancerous polyps.
About half of the participants received faecal occult blood tests, that analyse barely perceptible amounts of blood in patients' stools, and the other half underwent colonoscopies, using a flexible tube inserted into the bowel.
Six per cent of those who took the faecal test tested positive and went on for a colonoscopy.
Of those who went directly for a colonoscopy, 28 per cent had cancer or pre-cancer.
The faecal test has to be done every year, but it is cheaper and simpler. A colonoscopy is needed only once every 10 years.
Dr Martin Wong Chi-sang, director of the university's bowel cancer education centre, said Hongkongers were more ready to accept the faecal test than Westerners. He said 78 per cent of the participants returned for the test in the fourth year, while the rate of returnees was less than half in many Western countries.
Wu said the government could consider extending its screening subsidy to the private sector because of heavy pressure on the public health system.
The waiting time for patients with symptoms to receive a colonoscopy in public hospitals is one to two months for urgent cases and about 18 months for those less urgent.
The centre is recruiting another 5,000 participants aged between 40 and 70 for screening from now until February 16.