THE Cancer Science Institute of Singapore (CSI Singapore) has found a cheaper and safer way to treat advanced-stage cancer patients, by combining chemotherapy drug docetaxel with a common anti-fungal
The novel drug combination was administered to 31 breast-cancer patients in Singapore for the first time between July 2005 and September 2006 in a clinical trial.
They were given anti-fungal drug ketoconazole orally for three days prior to being injected with a lowered dose of docetaxel.
The result was fewer side effects, but with the same efficacy, as a standard dose of docetaxel, said Dr Lee
Soo Chin, the senior principal investigator of the study.
Docetaxel, an expensive drug used in chemotherapy for final-stage breast cancer, has side effects such as bone-marrow suppression, which causes bloodcell deficiency. The powerful drug is also known to lower the white blood-cell count in 70 per cent of patients, which can make patients more prone to infections.
Lowering the dose of docetaxel by 40 to 50 per cent and administering it with ketoconazole significantly reduced the occurrence of this side effect to 30 per cent, said Dr Lee.
Ketoconazole, a prescription drug that can be consumed in pill form, inhibits a natural enzyme in the human body that renders docetaxel inactive. Hence, when combined, doctors can reduce the dose of docetaxel.
The study also uncovered inter-ethnic differences in the way the two drugs reacted among Asian patients. Ketoconazole inhibited the enzyme most significantly among Chinese patients and the least for Indians, while Malay patients had intermediate results, said Dr Lee.
This meant that Indians needed more docetaxel to achieve the desired therapeutic drug level, while it had to
be administered with caution to Chinese patients.
Explaining the significance of this finding, Dr Lee said: “For the longest time, we treated patients based on data generated from Caucasian patients. But some of this data may not be applicable to Asian patients.”
A standard dose of docetaxel costs $1,800 to $2,500 and has to be administered every three weeks (one cycle) for four to six cycles, said Dr Lee, who is a breast-cancer oncologist and senior consultant at the department of haematology-oncology at the National University Hospital.
By reducing the dose of the pricey drug, patients are likely to pay $1,200 to $1,400 instead each time. The monthly Medisave withdrawal limit is capped at $1,200, she noted.
About 1,000 women are diagnosed with breast cancer each year, with the disease having already reached the final stage in 10 to 15 per cent of these women.
Docetaxel is not a cure for cancer, but keeps the cancer in check and helps prolong survival, said Dr Lee.