1978MO - Tumour-infiltrating macrophages, PD-L1 and tumour/stroma ratio as independent prognostic factors in a well-defined European cohort of patients with oral squamous cell carcinoma

Background

Currently, the most reliable prognostic factor for oral squamous cell carcinoma is the TNM classification system which stages cancers according to the tumour size and depth of invasion (T), the presence and extent of regional lymph node metastases (N), and the presence of distant metastases (M). Nevertheless, tumours of the same stage are heterogeneous with respect to aggressiveness and outcome. Therefore we aimed to study whether CD163+ tumour-infiltrating macrophages, programmed death-ligand 1 (PD-L1) expression, tumour-stroma ratio and tumour-infiltrating lymphocytes can provide supplementary prognostic information.

Methods

44 consecutive cases of surgically resected OSCC without neoadjuvant therapy were selected. Paraffin sections of the tumours were immunohistochemically stained for CD163 (Clone MRQ-26) and PD-L1 (clone 22C3). Numbers of CD163+ macrophages were counted, and PD-L1 tumour proportion score, immune cells score and combined positive score were determined. Tumour/stroma ratio and tumour-infiltrating lymphocytes were evaluated on haematoxylin-eosin stained sections.

Results

In multivariate analysis including classical prognostic factors, high numbers of CD163+ macrophages were associated with worse overall survival (≤ 24 months) (OR: 6.49; 95% CI: 1.04-40.60; p=0.045). PD-L1 tumour proportion score ≥ 5% was also associated with worse overall survival (OR: 9.67; 95% CI: 1.30-71.64; p=0.026) whereas no association between PD-L1 immune cells score or combined positive score and overall survival was observed. Moreover, tumour/stroma ratio ≥ 50% was associated with worse overall survival (OR: 25.97; 95% CI: 1.83-368.18; p=0.016). No association between tumour-infiltrating lymphocytes and survival was detected.

Conclusions

In our well-defined cohort of oral squamous cell carcinomas, a high number of CD163+ tumour-infiltrating macrophages, a PD-L1 tumour proportion score ≥ 5% and a tumour/stroma ratio ≥ 50% are independent prognostic factors for overall survival ≤ 24 months. These data can easily be included in clinical settings but should be confirmed in larger populations.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.