Seven leukaemia patients may have been cured after being treated with arsenic, it was claimed yesterday. The patients, aged between 21 and 44, also suffered no side effects when they were given quantities of the poison by doctors. Researchers in the department of medicine at the University of Hong Kong said that the results could signal a new way to treat other types of cancer. But Professor Kwong Yok-lam said more studies on arsenic were needed to see what other benefits it could have in treating diseases. He warned that it should only be used by doctors who knew how to treat people with it in controlled conditions. He said: 'Arsenic is a well-known poison . . . but relapsed leukaemia patients have been treated with it and the therapy has been uniformly successful. 'None of the patients has had any side effects. Testing by molecular biology has shown most to be potentially cured.' The arsenic treatment for the seven patients was launched at the beginning of last year.