Detecting overexpression of PD-L1 on circulating tumor cells (CTC) is feasible by assay and may have prognostic significance in head and neck squamous cell carcinoma (HNSCC), according to a study published in the Annals of Oncology.1

CTCs may be biomarkers for the risk of metastasis and residual disease, and their molecular characteristics may allow for new approaches to therapy management.

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Study authors developed an RT-qPCR assay to detect PD-L1 mRNA expression in EpCAM(+) CTC fractions. The study enrolled 113 patients with locally advanced HNSCC who were evaluated for PD-L1 expression at baseline, after 2 cycles of TPF [docetaxel, cisplatin, 5-fluorouracil] induction chemotherapy (IC), and after the end of concurrent chemo-radiotherapy.

All patients were treated with curative intent.

Over a quarter of patients showed overexpression of PD-L1 at baseline, 23.5% showed overexpression after IC, and 22.2% at the end of treatment.

Shorter progression-free survival (P = .001) and overall survival (P < .001) were observed among those with overexpression of PD-L1 at the end of treatment.

Patients without detected PD-L1 overexpression at end of treatment had a significantly complete response rate (odds ratio, 16; 95% CI, 2.76-92.72; P = .002).

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The authors concluded that this study “highlights the need to develop clear immune biological and clinical parameters that allow for rapid go/no-go decisions” for the treatment of HNSCC.


  1. Strati A, Koutsodontis G, Papaxoinis G, et al. Prognostic significance of PD-L1 expression on circulating tumor cells in patients with head and neck squamous cell carcinoma. Ann Oncol. 2017 Jul 4. doi: 10.1093/annonc/mdx206 [Epub ahead of print]