AB034. SOH24AB_195. An audit of prescribing practices of pertuzumab (Perjeta) in HER2+ breast cancer patients

Background: Pertuzumab, an anti-human epidermal growth factor receptor 2/3 (HER2/HER3) monoclonal antibody, has been demonstrated to be effective in the treatment of HER2-positive breast cancer. It was initially licensed in Ireland for the treatment of metastatic breast cancer in 2015, but is now also used in the neoadjuvant and adjuvant settings for primary breast cancer with high-risk features for recurrence. The aim was to assess current prescribing practices of pertuzumab (Perjeta) in HER2+ breast cancer patients in one of the eight Irish designated cancer surgical centres, which is also an Organisation of European Cancer Institutes (OECI)-accredited cancer centre.

Methods: All patients who had been administered Pertuzumab in Beaumont Hospital (Dublin) between the period 2015–2023 were included. Data were collected using a prospectively-maintained dispensing database in Department of Pharmacy of the hospital and cross referenced with a prospectively-maintained breast cancer database in the Department of Surgery.

Results: A total of 75 patients were identified that had undergone treatment with pertuzumab over an 8-year period. Thirty-two of these were treated in the 5 years prior to the approval of treatment in the neoadjuvant setting and 43 in the 3 subsequent years. The average number of doses administered per patient was 14.56. The average number of doses administered during the time period that pertuzumab was only approved for metastatic patients [2015–2019] was 23.9, in comparison to 8.4 following the introduction of treatment for curative intent (2019–present). Patients treated for metastatic disease received on average 34 months of pertuzumab.

Conclusions: Pertuzumab usage in this single-institution study has risen predictably since its first regulatory approval in 2015, with a significant increase in prescribing since its approval for use in the neoadjuvant setting. In this institution, patients treated with pertuzumab for metastatic disease are surviving on average nearly 3 years on maintenance treatment. This infers a positive impact on the survival of patients with metastatic breast cancer, but also highlights the significant cost implications for ongoing treatment. This audit will help inform future pharmacoeconomic evaluations aimed at further improving the survival prospects of all HER2-positive breast cancer patients.

Keywords: Breast cancer; human epidermal growth factor receptor 2 positive breast cancer (HER2 positive breast cancer); pertuzumab; metastatic breast cancer; Perjeta