Abstract P1-21-03: Efficacy of tyrosine kinase inhibitors (TKI) in the treatment of patients with HER2-positive (HER2+) breast cancer with or without brain metastases: A systematic review and meta-analysis
Authors: Nader-Marta Guilherme , Martins-Branco Diogo , Agostinetto Elisa , Bruzzone Marco , Ceppi Marcello , Lambertini Matteo , Kotecki Nuria , Awada Ahmad , de Azambuja Evandro 
Published: March 2022

Abstract
BACKGROUND: Brain metastases (BM) occur in up to 50% of patients (pts) with HER2+ metastatic breast cancer (MBC) and are associated with high morbidity and mortality. While the treatment outcomes of patients (pts) without BM are largely determined by their extra-cranial activity, the outcomes of pts with BM are also influenced by the treatment’s activity in the central nervous system (CNS). TKI-based regimens, have been incorporated into the management of pts with HER2+ MBC. This systematic review aims to assess the clinical outcomes of in pts with or without BM treated with TKI-containing regimens vs those treated with non-TKI-containing regimens. METHODS: A systematic literature search of PubMed, Embase, CENTRAL, and conference proceedings (ASCO, SABCS, ESMO, and ESMO Breast) up to June 20, 2021, was conducted to identify randomized clinical trials (RCT) comparing systemic therapies with anti-HER2 TKI-containing regimens and non-TKI-regimens in pts with HER2+ MBC (PROSPERO ID: CRD42021252332). Studies were screened for the availability of data on progression-free survival (PFS) and overall survival (OS) in subgroups of pts with and without BM at baseline. A random-effect model was used to calculate PFS and OS, reported as pooled hazard ratio (HR) with 95% confidence intervals (CI). The Higgins I2 index was used to evaluate the heterogeneity between studies. To assess whether the pooled HRs estimates were stable or strongly dependent on one or few studies, sensitivity analyses were conducted by interactively recalculating the pooled HRs estimates after exclusion of each single study. RESULTS: Of 1,671 identified records, 5 RCT were included involving 2,437 pts (490 with and 1,947 without BM at baseline). Intervention arms included tucatinib, lapatinib, pyrotinib or afatinib in combination with cytotoxic chemotherapy ± trastuzumab; control arms included cytotoxic chemotherapy ± trastuzumab or T-DM1. No trial evaluating neratinib met inclusion criteria. All trials allowed the inclusion of pts with stable and asymptomatic BM, while one (HER2CLIMB) also included pts with progressing/untreated BM. Previous treatment with trastuzumab was reported in 92.8% (n=2,262) of the pts. Regarding PFS, a non-statistically significant trend favoring TKI-containing regimens was observed both in pts with BM (HR 0.67, 95% CI 0.41-1.12, p=0.13) and without BM (HR 0.55, 95% CI 0.24-1.26, p=0.16). Substantial heterogeneity was detected in both subgroups (I2 = 64.4%, p=0.024 and I2 = 95.6%, p 0.001, respectively). Sensitivity analysis, excluding each study one by one, demonstrated a significant PFS benefit favoring TKI-containing regimens in pts with BM after the exclusion from the analysis of afatinib (Lux-Breast1), a non-HER2-specific TKI (HR 0.56, 95% CI 0.35-0.90, p=0.016), with no significant heterogeneity (I2 = 46.9%, p=0.13). Regarding OS, a non-statistically significant trend favoring non-TKI regimens was observed both in pts with BM (HR 1.28, 95% CI 0.48-3.40, p=0.62) and without BM (HR 1.02, 95% CI 0.53-1.98, p=0.94). Substantial heterogeneity was detected in both subgroups (I2 = 86.8%, p=0.001 and I2 = 85.7%, p=0.008, respectively). Sensitivity analysis showed no significant impact on OS after exclusion of each study one by one. No publication bias was detected by Egger’s test. CONCLUSION: Our results suggest a similar magnitude of OS and PFS benefit from anti-HER2 TKI-containing regimens in pts with or without BM. Sensitivity analysis including only trials that evaluated regimens containing tucatinib, lapatinib or pyrotinib demonstrated a significant PFS benefit favoring TKI-containing regimens in pts with BM, emphasizing the relevance of CNS involvement for the interpretation of the results of studies evaluating this class of agents.
Citation Format: Guilherme Nader-Marta, Diogo Martins-Branco, Elisa Agostinetto, Marco Bruzzone, Marcello Ceppi, Matteo Lambertini, Nuria Kotecki, Ahmad Awada, Evandro de Azambuja. Efficacy of tyrosine kinase inhibitors (TKI) in the treatment of patients with HER2-positive (HER2+) breast cancer with or without brain metastases: A systematic review and meta-analysis [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-21-03.