Doctors are worried an increasing number of cancer patients are giving up conventional treatment for alternative therapies. The director of the cancer research centre at Queen Mary Hospital, Professor Raymond Liang Hin-suen, said there should be tighter control over alternative treatments which included drugs, herbs and other therapies. He said more people were seeking alternative help, which might postpone a conventional cure. 'Although we welcome any curiosity and tests into all possibilities of fighting against cancers, there is no scientific evidence that they work,' said Professor Liang, chief of haematology and oncology. 'The patients who turned to unproven treatments without understanding will risk losing money and the chance of being cured.' The warning came as Dr William Lane, who pioneered research into the use of shark cartilage for treating cancer, gave talks in Hong Kong to promote the therapy. Dr Lane said a number of shark cartilage tablets had been sold in the territory but many people misused the product. 'They do not take the right dosage and many of the products had been made from substandard cartilage,' said Dr Lane, adding that his pictures and name had been exploited by brands unrelated to him. He said clinical trials would soon be carried out with medical authorities in China and Taiwan to prove the effectiveness of the substance, which had been endorsed by the US as non-toxic. Deputy chief executive of the Consumer Council, Li Kai-ming, said although drugs for alternative therapies were banned from advertising, selling had been done through direct marketing. 'Wrong or exaggerated information passed through word of mouth would also be subject to police investigations,' he said.