What is the optimal duration of adjuvant trastuzumab?

Two years versus 1 year of adjuvant trastuzumab does not confer any advantage,19while 6 months of adjuvant trastuzumab failed to show non-inferiority compared to 1 year.20Until data from other studies comparing a shorter duration versus 1 year of adjuvant trastuzumab become available, the standard duration for adjuvant trastuzumab is 1 year. Cost-Effectiveness Analyses The cost-effectiveness of adjuvant trastuzumab is approximately USD $27,790 per additional quality adjusted life years (QALY) gained for the 3-weekly regimen based on estimates from the NICE evidence review group.16Other scenarios modelled on this estimate by the same group gave incremental costs per QALY gained ranging from USD $24,700 toUSD $50,950. A study based on local societal costs and benefits found that average cost per QALY was USD $19,175 (median: USD $18,994) in 2005. 21

Pertuzumab is a monoclonal antibody which binds to the dimerisation domain of HER2. When combined with trastuzumab and a taxane-based chemotherapy, the addition of pertuzumab has been shown to increase pathological complete response rate in the neoadjuvant setting22and improve overall survival in the metastatic setting23for HER2 positive breast cancer. Given the above data, the latest NCCN Clinical Practice Guidelines in Oncology Breast Cancer version 2.2015 considers it reasonable to incorporate pertuzumab concurrently with trastuzumab and a taxane into the adjuvant therapy for patients with T2 or N1 HER2 positive breast cancer who did not receive prior neoadjuvant pertuzumab.14Given the absence of direct evidence of benefit from adjuvant pertuzumab, the overwhelming majority of the SCAN breast cancer workgroup members do not endorse this recommendation. The workgroup notes the ongoing APHINITY trial which is assessing the addition of a pertuzumab to chemotherapy and trastuzumab in the adjuvant setting.24If the results are positive and the use of pertuzumab is incorporated in other international guidelines, the SCAN guidelines will be amended accordingly in the future.

Lastly, subcutaneous trastuzumab has been found to be non-inferior to intravenous trastuzumab in terms of efficacy, pharmacokinetic profile and safety. 25The workgroup will await incorporation of this product in international guidelines before further assessment of its applicability in the local context.