P11.39.B IMPORTANCE OF THE HISTOLOGICAL GROWTH PATTERN IN BRAIN METASTASES. A PROSPECTIVE IMAGING-GUIDED BIOPSY TRIAL

Abstract BACKGROUND The histological growth pattern (HGP) of liver metastases is frequently evaluated, while the same attention is often absent for brain metastases despite evidence suggesting its prognostic significance. This oversight may stem from the lack of a standardized method for assessing the HGP at the macro-metastasis/brain parenchyma interface (MMPIbrain). This is the first prospective, image-guided trial aimed at standardizing the collection and analysis of HGP at the MMPIbrain. MATERIAL AND METHODS We recruited 50 patients (21 female, 29 male, median age 62.2 years) undergoing microsurgical resection of a lesion suspicious for a BM. The most frequent primary tumor was lung cancer (n = 23; 46%). Based on the previous trials, our protocol consisted of 4 elements: determination of target areas on the preoperative MRI scan, which appeared suspicious for tumor cell infiltration; identification of these target areas using the neuronavigation system; employment of fluorescein sodium (FL) as a tracer to detect tumor borders; use of laser confocal endomicroscopy for direct visualization of the MMPI intraoperatively. A minimum of at least 70% successful MMPI-specific tissue acquisition was determined as a primary endpoint. RESULTS The protocol achieved successful tissue acquisition from the MMPIbrain in 93.2% of patients, meeting the study’s primary endpoint. Exploratory analyses indicated that patients with infiltrative HGPs had a significantly worse survival outcome compared to those with non-infiltrative patterns. Notably, all patients who developed meningeal metastasis had infiltrative HGPs. Pre-operative MRI patterns strongly correlated with infiltrative HGPs, and the laser confocal endomicroscopy accurately visualized the MMPIbrain intraoperatively. CONCLUSION Our neurosurgical protocol was feasible and confirmed the clinical impact of infiltration at the MMPIbrain, supporting the necessity to include it in routine pathological reports for the benefit of patients with BM. In addition, this highlights the potential importance of supramarginal resection in brain metastases with an infiltrative HGP.