Abstract P2-01-06: Real-world outcome and cost analysis of the addition of pertuzumab to neoadjuvant therapy in localized HER2 positive breast cancer: a single center experience
Authors: Panet Francois , Young Matt , Wong Stephanie , Dragomir Alice , Rose April A. N. , Panasci Lawrence 
Published: March 2023

Abstract
BACKGROUND: Breast cancer is the most common cancer in woman and can be classified based on the expression of hormonal receptor as well as the human epidermal growth factor receptor 2 (HER2). HER2 amplification is associated with an aggressive clinical course and higher recurrence rates following curative intend surgery. For non-metastatic T2 or node-positive HER2-positive disease neoadjuvant treatment is favored. The National Comprehensive Cancer Network (NCCN) guidelines have endorsed the use of dual HER2 blockage with trastuzumab and pertuzumab combined with chemotherapy in the neoadjuvant setting. However, pertuzumab isn’t frequently reimbursed in public health care systems for this indication. Patients who don’t achieve a pathological complete response (pCR) at surgery are eligible for adjuvant T-DM1, adding significant side effects on patients and cost on the healthcare system.
METHODS: We conducted a retrospective analysis of patients receiving anti-HER2 therapy in the neoadjuvant setting at the Jewish General hospital between 2015 and 2021. After 2019, pertuzumab was routinely added to standard neoadjuvant therapy enabling us to compare patients treated with or without dual-HER2 blockade. Our primary endpoint is the percentage of pCR at surgery. Secondary objectives are to estimate and compare the cost of anti-HER2 targeted therapy in the perioperative setting and side effect burden on patients. Statistical analyses were done using fisher exact test with statistical significance defined p value &lt; 0.05 in a one-sided test. Drug cost was calculated using publicly available resources.
RESULTS: We identified 83 patient who underwent neoadjuvant chemotherapy for HER2 amplified breast cancer. 44 patients received only trastuzumab has anti-HER2 therapy and 39 patients were treated with dual HER2 blockade containing pertuzumab. The addition of pertuzumab was associated with improved the pCR rate (67% vs. 27%; p = 0.0016). The increased pCR rate was observed in hormone-receptor positive and negative tumors. We also described a non-statistically significant trend in reduction in the requirement for axillary dissection with the use of pertuzumab (28% vs. 39%; P=0.2208). The increased in pCR rate with pertuzumab reduced the number of patients eligible for adjuvant T-DM1. If all patients with residual disease had received adjuvant T-DM1, the cost of neoadjuvant pertuzumab would be neutral, with a mean anti-HER2 drug cost of 65 150 CA$ in the pertuzumab-trastuzumab group and 66 116 CA$ in the trastuzumab group.
CONCLUSION: Our real-world analysis confirmed that neoadjuvant chemotherapy with dual HER2-blockade was well tolerated and associated with increased the pCR rate compared to regimens containing trastuzumab only. This measure is neutral on drug cost by reducing the amount of patients eligible for adjuvant T-DM1. Further research is warranted to estimate the overall health-care utilization costs of neoadjuvant pertuzumab-trastuzumab in settings where adjuvant T-DM1 is available.
Table 3: Pathologic complete response (pCR) and type of surgery in patients who received dual HER2 blockade with neoadjuvant pertuzumab-trastuzumab plus chemotherapy and in patients receiving trastuzumab only with chemotherapy at Jewish General Hospital between 2015 and 2021. ** p &lt; 0,01, ns non-statistically significant
Citation Format: Francois Panet, Matt Young, Stephanie Wong, Alice Dragomir, April A. N. Rose, Lawrence Panasci. Real-world outcome and cost analysis of the addition of pertuzumab to neoadjuvant therapy in localized HER2 positive breast cancer: a single center experience [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-01-06.