Author Identifier

James Freeman Orcid: Ashleigh McEvoy Orcid: Johnny Lo Orcid: Mel Ziman Orcid: Elin Gray Orcid:

Document Type

Journal Article

Publication Title

The oncologist



PubMed ID





School of Medical and Health Sciences / School of Engineering



Grant Number

NHMRC : 1013349


Khattak, M. A., Reid, A., Freeman, J., Pereira, M., McEvoy, A., Lo, J., ... & Amanuel, B. (2019). PD-L1 Expression on Circulating Tumor Cells May Be Predictive of Response to Pembrolizumab in Advanced Melanoma: Results from a Pilot Study. The oncologist. Advance online publication.


BACKGROUND: PD-1 inhibitors are routinely used for the treatment of advanced melanoma. This study sought to determine whether PD-L1 expression on circulating tumor cells (CTCs) can serve as a predictive biomarker of clinical benefit and response to treatment with the PD-1 inhibitor pembrolizumab.

METHODS: Blood samples were collected from patients with metastatic melanoma receiving pembrolizumab, prior to treatment and 6-12 weeks after initiation of therapy. Multiparametric flow cytometry was used to identify CTCs and evaluate the expression of PD-L1.

RESULTS: CTCs were detected in 25 of 40 patients (63%). Patients with detectable PD-L1

CONCLUSION: Our results reveal the potential of CTCs as a noninvasive real-time biopsy to evaluate PD-L1 expression in patients with melanoma. PD-L1 expression on CTCs may be predictive of response to pembrolizumab and longer PFS.

IMPLICATIONS FOR PRACTICE: The present data suggest that PD-L1 expression on circulating tumor cells may predict response to pembrolizumab in advanced melanoma. This needs further validation in a larger trial and, if proven, might be a useful liquid biopsy tool that could be used to stratify patients into groups more likely to respond to immunotherapy, hence leading to health cost savings.



Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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