Lapatinib DitosylateTykerb

ICER varied widely depending on assumed extent of substitution of lapatinib for continued trastuzumab treatment; range given is for 50% trastuzumab 'continuers' scenario. ICER was dominant (less costly and more effective) under assumption of 80% continuing trastuzumab use.

For example, a proportion of 50% trastuzumab 'continuers' results in a cost per QALY in the range $75,000 to $105,000. PBAC · 2007

PopulationPatients with HER2-positive metastatic breast cancer who have received prior therapy with anthracycline and taxane, and whose disease progresses despite trastuzumab or who meet trastuzumab-exemption criteria (early recurrence within 12 months of adjuvant trastuzumab, or CNS metastases)

• uncertain proportion of patients continuing trastuzumab despite progression in Australian clinical practice (critical to ICER calculation), small and potentially biased Australian Oncology Monitor sample (n=51), stability and representativeness of AOM data unclear, difficulty reconciling assumption that lapatinib stops at progression while trastuzumab continues, immature overall survival data (not statistically significantly different from capecitabine monotherapy), insufficient evidence that Government savings will be realised

Label narrower than PBS population — PBAC restricts to initial treatment and includes trastuzumab-exemption criteria; TGA label requires prior trastuzumab progression only.