Abstract PO1-17-08: Post-approval treatment patterns and tolerability of neratinib in HER2+ early-stage breast cancer

Abstract Background: While the approval status for neratinib in HER2+ early-stage breast cancer (EBC) allows its use following any trastuzumab-based therapy, the phase 3 ExteNET trial (NCT00878709), which yielded an improvement in disease-free survival, was conducted when single-agent adjuvant trastuzumab was standard of care (SOC) and before approvals of adjuvant pertuzumab + trastuzumab (FDA-approved 2017) or trastuzumab emtansine (T-DM1; FDA-approved 2019). Given recent changes in SOC for HER2+ EBC, health care professionals may seek contemporary and real-world information regarding treatment patterns and tolerability of neratinib. Methods: A literature review was performed to identify studies that characterized trends in use of extended adjuvant neratinib in HER2+ EBC. Due to differences in study design (interventional, observational, claims data) and populations studied, a descriptive summary of data is presented in lieu of statistical cross-study comparisons. Results: Following FDA approval of neratinib in HER2+ EBC in 2017, five studies have reported treatment patterns of extended adjuvant neratinib in a clinical trial or real-world setting; three studies included safety data (Table 1). In the phase 2 CONTROL trial (NCT02400476; N=563; 2015–2021), approx. 82%, 17%, and 1% of neratinib-treated pts received prior adjuvant trastuzumab, pertuzumab, or T-DM1, respectively, and prior neoadjuvant/adjuvant pertuzumab did not affect rates of grade ≥3 diarrhea, diarrhea-related discontinuations, or treatment duration.1 In an interim analysis of the observational ELEANOR study (NCT04388384; N=187; 2020–ongoing), approx. 41%, 33%, and 19% of neratinib-treated pts received prior adjuvant trastuzumab (as their only anti-HER2 treatment), pertuzumab + trastuzumab, or T-DM1, respectively; corresponding rates of grade ≥3 diarrhea were 19%, 25%, and 14%, respectively, with no new safety signals reported.2 In a chart review from the US Oncology Network (N=166; 2017–2020), approx. 99%, 43%, and 2% of neratinib-treated pts received prior adjuvant trastuzumab (56% as their sole anti-HER2 treatment), pertuzumab, or T-DM1, respectively.3 Diarrhea was mainly moderate (29%; n=43/150) or mild (22%; n=33/150), with few severe cases (1%; n=2/150).3 In a retrospective analysis employing the IQVIA claims database (N=385; 2017–2021), prior use of recently approved adjuvant agents increased over time, with rates of prior pertuzumab + trastuzumab or prior T-DM1 as high as 52% and 14%, respectively, in 2020.4 In the Neat-HER virtual registry (N=46; 2018–2021), approx. 41% and 11% of neratinib-treated pts received prior adjuvant pertuzumab or T-DM1, respectively.5 Conclusions: Recent studies have observed neratinib use in clinical practice following adjuvant trastuzumab-based therapy including pertuzumab + trastuzumab or T-DM1. Preliminary data suggest a similar safety profile for pts with/without prior pertuzumab. These datasets are limited by the fact that: (1) some pts were enrolled in the CONTROL trial prior to launch of adjuvant T-DM1 and pertuzumab; (2) the interval between T-DM1 launch in Europe and start of the ELEANOR study was relatively short; and (3) not all toxicity measures were formally graded. A summary of available safety and effectiveness results is forthcoming. Additional interventional and non-interventional studies will continue to evaluate the safety and effectiveness of neratinib following current SOC adjuvant therapy in HER2+ EBC. Table 1. Treatment patterns of HER2-targeted adjuvant agents preceding neratinib use in HER2+ EBC ITT, intent-to-treat; T-DM1, ado-trastuzumab emtansine. aTherapies were recorded as used for adjuvant therapy in CONTROL, ELEANOR, US Oncology, and Neat-HER. CONTROL includes unpublished data. In the IQVIA claims analysis, HER2-targeted agent(s) used within 12 months prior to neratinib initiation were assumed to be adjuvant therapies. Pertuzumab use was generally taken in combination with trastuzumab as dual HER2 blockade and some pts received more than one anti-HER2 adjuvant treatment, for example T-DM1 in addition to pertuzumab plus trastuzumab. bAdjuvant trastuzumab monotherapy or in combination with chemotherapy unless noted otherwise. cThe proportion of patients who took at least one tablet of neratinib for ≥75% of the prescribed treatment days and did not take neratinib on days when neratinib was not prescribed. dData forthcoming. eIncludes prior trastuzumab monotherapy and trastuzumab used in combination with pertuzumab; 93/166 pts (56%) received trastuzumab as their only anti-HER2 agent (monotherapy or in combination with chemotherapy; unpublished data). fIncludes prior trastuzumab monotherapy as well as trastuzumab used in combination with pertuzumab. References Citation Format: Kelly McCann, Nadia Harbeck, Debu Tripathy, Arlene Chan, Jay Andersen, Joyce O'Shaughnessy, Gregory Vidal. Post-approval treatment patterns and tolerability of neratinib in HER2+ early-stage breast cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-17-08.