Relationships Between Apparent Diffusion Coefficient (ADC) Histogram Analysis Parameters and PD-L 1-expression in Head and Neck Squamous Cell Carcinomas: A Preliminary Study

BACKGROUND: Immunotherapy has become a cornerstone of the modern cancer treatment. It might be crucial to predict its expression non-invasively by imaging. The present study used diffusion-weighted imaging (DWI) quantified by whole lesion apparent diffusion coefficient (ADC) values to elucidate possible associations with programmed cell death ligand 1(PD-L1) expression in head and neck squamous cell cancer (HNSCC). PATIENTS AND METHODS: Overall, 29 patients with primary HNSCC of different localizations were involved in the study. DWI was obtained by using a sequence with b(-)values of 0 and 800 s/mm(2) on a 3 T MRI. ADC values were evaluated with a whole lesion measurement and a histogram approach. PD-L1 expression was estimated on bioptic samples before any form of treatment using 3 scores, tumor positive score (TPS), immune cell score (ICS), and combined positive score (CPS). RESULTS: An inverse correlation between skewness derived from ADC values and ICS was identified (r = -0.38, p = 0.04). ADC(max) tended to correlate with ICS (r = -0.35, p = 0.06). Other ADC parameters did not show any association with the calculated scores. CONCLUSIONS: There is a weak association between skewness derived from ADC values and PD-L1 expression in HNSCC, which might not be strong enough to predict PD-L1 expression in clinical routine. Presumably, ADC values are more influenced by complex histopathology compartments, comprising cellular and extracellular aspects of tumors than only of a single subset of tumor associated cells.