SRS395 - Antitumoral immunity in colorectal liver metastases- histopathological growth patterns and tertiary lymphoid structures

Abstract Background Tertiary lymphoid structures (TLSs) and histopathological growth pattern (HGP) are potential prognostic histological features of cancer. We investigated their prognostic value in patients with colorectal cancer liver metastases (CRCLM). Methods 133 patients with CRCLM treated by surgical resection from two cancer centres were categorized into desmoplastic (d) and non-desmoplastic (nd) HGP cohorts along with presence/absence of TLS (+/-). Multiplex immunohistochemical staining using 13 immune cell markers was used to determine the cellular composition and spatial distribution of TLSs. Results Patients with CRCLM demonstrating dHGP (n = 54) had improved overall survival compared to patients with ndHGP (n = 79) (Hazard ratio (HR) = 0.53 (0.29–0.93), P = 0.034, log-rank test). Similarly, patients with TLS+ CRCLM (n = 65) showed improved survival compared to those with TLS- CRCLM (n = 68) (HR = 0.51 (0.29–0.90), P = 0.04). On assessment of four patient groups (dHGP/ TLS+ (n = 28), dHGP/ TLS- (n = 26), ndHGP/TLS+ (n = 37), ndHGP/ TLS-(n = 42), there was added prognostic value with absence of both dHGP and TLS having worse prognosis (P = 0.05, chi-square = 7.67, df = 3). Further analysis to interrogate TLS maturation and activity along with spatial distribution is underway to understand their prognostic impact. Conclusions The presence of HGP and TLS individually have prognostic value with added benefit of combining the two parameters. Further evaluation is underway to assess the underlying.