Prognostic Role of PD-L1 and IDO-1 Expression in Sinonasal Carcinoma

Sinonasal carcinomas (SNC) are rare, aggressive tumours with complex immunological aspects. Still, prognostic markers are missing. The study aimed to investigate the relationship between immune checkpoints - specifically programmed death-ligand 1 (PD-L1) and Indolamin-2,3-dioxygenase 1 (IDO-1) - and clinical parameters in SNC.

In this monocentric study immunohistochemical analysis of the checkpoints PD-L1 and IDO-1 was carried out retrospectively in 85 SNC patients from 2004 to 2018. Tumour proportion score (TPS), combined positive score (CPS) and combined IDO-1 score classified the PD-L1 and IDO-1 expression. The study was conducted in a specialized tertiary care centre, indicating comprehensive multidisciplinary care with surgical, radiotherapeutic, and systemic treatment intervention.

Over a median observation period of 41 months, 52 squamous cell carcinomas (SCC, 61%) and 33 adenocarcinomas (AC, 39%) were included. A total of 31 patients (37%) were classified in UICC IV, 89.4% (n = 76) received a primary resection. Three-year progression-free survival (PFS)/overall survival (OS) rates were 63.6%/81.4% in SCC and 73.1%/82.5% in AC, respectively. Sinonasal AC showed significantly more frequently negative PD-L1 expression and CPS <1 compared to sinonasal SCC (p = 0.035, p = 0.002). Sinonasal SCC with TPS score >50%, combined low IDO-1 score and high UICC stage showed significantly worse 3-year PFS and OS values (p < 0.05).

The study identifies PD-L1 and IDO-1 as possible prognostic factors for sinonasal SCC, but less so for sinonasal AC. A TPS score >50% and combined low IDO-1 score correlate with shortened 3-year PFS and OS in sinonasal SCC. Immune checkpoints could, therefore, represent important target molecules for the prognosis assessment of sinonasal SCC.