Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Taxotere (Rhone-Poulenc Rorer)
vials containing 20 mg/0.5 mL and 80 mg/2 mL for dilution
Indication: cancer chemotherapy
The anticancer drug paclitaxel is derived from the bark of the pacific yew tree. Docetaxel is obtained from the young shoots of the tree. The two drugs have not been approved for identical indications, although they can both be used to treat metastatic breast cancer when previous therapy has been unsuccessful. Docetaxel is also approved for the treatment of patients with locally advanced or metastatic non-small cell lung cancer.
The drug is given as a one-hour infusion every 3 weeks. High intracellular concentrations are thought to result in disruption of the micro tubular network which is essential for mitosis. The drug is metabolised and most of the metabolites are excreted in the faeces within 48 hours.
Docetaxel can be used to treat locally advanced or metastatic non-small cell lung cancer. In previously untreated patients, the response rate is 31% compared with 19% in patients who have received treatment with platinum. Unfortunately, survival is only likely to be increased by a few months, but this may be important in a disease with a very poor prognosis.
Patients with locally advanced or metastatic breast cancer who do not respond to anthracycline also have a poor prognosis. Approximately half these patients will respond to docetaxel. The median duration of response is 27 weeks.
Docetaxel is cytotoxic and has many adverse effects. A severe neutropenia occurs in 75% of patients and can lead to fatal infections. Most patients will lose their hair and over 60% will develop rashes. Fluid retention also occurs in more than 60% of patients. It may present as oedema or effusions and is cumulative in incidence and severity. The onset of this adverse effect may be delayed if the patient begins oral steroids before each treatment. This premedication may also reduce the incidence and severity of the hypersensitivity reactions which occur in over 30% of patients.
As paclitaxel is a very expensive drug (over $1300 for 150 mg), the results of a comparative study of paclitaxel and docetaxel will be welcome.