Doctors have been asked to switch to a new hormone treatment for breast cancer patients after a global study showed it can reduce the risk of recurrence by as much as 4 per cent over existing treatment. Expert Dr Louis Chow Wing-cheong - quoting the global Intergroup Exemestane Study - said the rate of recurrence after the use of anti-aromatase inhibitors was 15 per cent, against 19 per cent in the case of the traditional therapy, using the drug tamoxifen. Anti-aromatase agents are a new class of hormonal agents recently approved for the treatment of women with breast cancer. They work by reducing levels of the female hormone oestrogen, denying cancer cells a growth stimulant. The lifetime risk for women of developing breast cancer around the world is one in seven. In Hong Kong, breast cancer accounted for 22 per cent of all new cancers in females diagnosed in 2003. In 2004, 454 women died from this cancer, almost 10 per cent of all cancer deaths in females. Dr Chow, an executive committee member of the Asian Breast Cancer Society, yesterday said the new treatment was especially recommended for postmenopausal breast cancer patients. A member of the Hospital Authority's task group on breast cancer management, he said anti-aromatase inhibitors had been approved in more than 40 countries and were recommended in major medical guidelines overseas. The Intergroup study found 13 per cent of patients treated with the new agent had complained of arthralgia - or pain in the joints - compared with 8 per cent for those treated with tamoxifen. However, Dr Chow maintained the difference was statistically insignificant. The 56-month global study covered 4,724 patients in 37 countries, including Hong Kong. Dr Chow said a separate clinical study in Hong Kong involving 90 patients also showed the new agent could help reduce the size of tumours before surgery.