BROTHERS can be reluctant when it comes to sharing, but when two-year-old Leung Man-chun needed special blood cells to battle leukaemia, his big brother came to the rescue. Eleven-year-old Leung Man-yiu's bravery would have cost him a painful operation under general anaesthetic and at least one night in hospital - but for a breakthrough technique being developed by Prince of Wales Hospital doctors. The new technique allows doctors to 'harvest' huge amounts of Man-yiu's vital stem cells, which produce red blood cells, white cells and platelets, and inject them into his little brother. Children's Cancer Centre consultant paediatrician Dr Li Chi-kong said specialists could now bombard Man-chun's bone marrow with high doses of chemotherapy and radiotherapy, then transfuse millions of his brother's life-giving cells into his body. The stem cells would regenerate and multiply, replacing those which had been bombarded with radiation, and being drawn into the bone marrow. 'For a traditional bone marrow harvest, the patient has to be sent to the operating room and have several punctures in the back, which is quite a painful procedure,' Dr Li said. 'With our new technique, we can actually get the [usually low] number of cells in the blood stream to an adequate amount to transplant. The donor can just sit in a room, watching television with the blood being taken. 'We stimulate the donor [with injections of growth enhancer] to get these stem cells, so the number of cells is much greater and recovery is much faster. The faster the recovery, the fewer complications,' Dr Li said. Usually such a transfusion would reap about eight million stem cells. With the growth enhancer, doctors can collect 80 million. The Leung brother are only the third - and latest - pair in Hong Kong to undergo the revolutionary treatment. A two-year-old boy received cells from his 10-month-old sister in April and a six-year-old boy dosed up on cells from his 11-year-old brother in June. All were doing well and Man-chung will go home this week, Dr Li said. 'We have to select the patients very carefully to see who will benefit the most,' he said. Parents have difficulty donating, because each possesses only some of the genes needed in their children's bone marrow. Siblings have a one-in-four chance of matching. Hundreds of bone marrow transplants have been carried out in Hong Kong, but the new method - in which the donor spends a few hours attached to a machine which selects only stem cells - opens the gateway to future techniques. 'So far, this has only been done in a very small number of centres in North America and Europe, and the reports I have come across are all of adults,' Dr Li said. 'We hope that in the future, we may be able to stop bone marrow harvesting so that donors will not have to go into the operating room for a painful procedure,' he added.