Readers are invited to write in with their questions about decisions of the Pharmaceutical Benefits Advisory Committee (PBAC). Australian Prescriber publishes selected questions from readers, together with answers from the PBAC. Questions may address issues such as regulatory decisions, pharmaceutical benefits listings and withdrawals.
This exclusive arrangement helps Australian Prescriber readers understand how the contents of the Pharmaceutical Benefits Scheme (PBS, see www.pbs.gov.au) are determined.
Letters and responses are reviewed by the Editorial Executive Committee and may be edited before publication. It may not be possible to reply to all individual questions.
Your questions to the PBAC
The listing of trastuzumab on the Pharmaceutical Benefits Scheme (PBS) in October 2006 was heralded with much fanfare. Along with this listing, changes to the prescribing requirements for taxanes also occurred. Both docetaxel and paclitaxel are now available on authority prescription for the treatment of HER2 positive early breast cancer in combination with trastuzumab. However, one group of patients will miss out on subsidised treatment. They are women with HER2 positive metastatic breast cancer who have not previously been treated with chemotherapy.
Patients with HER2 positive metastatic breast cancer can access trastuzumab under the Herceptin Access Program run through Medicare Australia. The prescribing restrictions for this program specify that the trastuzumab is to be used as a single drug or in combination with a taxane. Herein lies the problem. The current listing for taxanes on the PBS is 'advanced breast cancer after failure of prior therapy, which includes an anthracycline'. Patients with HER2 positive metastatic breast cancer who are chemotherapy naive cannot have the optimal therapy of trastuzumab in combination with a taxane, as the latter is not funded by the PBS.
Why were the taxanes made available for HER2 positive early breast cancer and not simply for all patients with HER2 positive breast cancer?
The Pharmaceutical Benefits Advisory Committee (PBAC) made its recommendation to subsidise taxanes for the treatment of HER2 positive early breast cancer in combination with trastuzumab because of evidence that this treatment combination met the requirements for PBS listing. The PBAC also recommended that the taxanes, in combination with an anthracycline and cyclophosphamide, be made available for adjuvant treatment for all patients with node positive breast cancer. Again this recommendation was made on the basis of evidence which showed that this treatment was of acceptable efficacy, safety and cost-effectiveness.
To date, the PBAC has not been presented with evidence to show that the combination of a taxane and trastuzumab in chemotherapy naive patients with metastatic breast cancer meets the requirements for PBS listing. While it may seem reasonable to extend the listing for the taxanes for HER2 positive early breast cancer to include all HER2 positive breast cancer, the efficacy and cost-effectiveness is not necessarily the same in metastatic breast cancer as when the treatment is used in early breast cancer.
The continuing success of the PBS depends upon a rigorous evidence-based assessment of drugs for subsidy. These requirements apply in all cases and ensure consistency and fairness in the listing process.