332PD - Change of PD-L1 expression status of high grade glial tumors at recurrence and its effect on survival

Date 09 September 2017
Event ESMO 2017 Congress
Session CNS tumours
Topics Central Nervous System Malignancies
Translational Research
Presenter Basak Oyan
Citation Annals of Oncology (2017) 28 (suppl_5): v109-v121. 10.1093/annonc/mdx366
Authors B. Oyan1, S. Eren2, O. Sonmez1, F. Ozkan3, K. Yaltırak4, U. Ture4
  • 1Medical Oncology, Acibadem University School of Medicine, 34662 - Istanbul/TR
  • 2Internal Medicine, Yeditepe University Hospital, 34752 - Istanbul/TR
  • 3Pathology, Yeditepe University Hospital, 34752 - Istanbul/TR
  • 4Neurosurgery, Yeditepe University Hospital, 34752 - Istanbul/TR

Abstract

Background

Although immunotherapy is not an established treatment option in high grade glial tumors, trials are ongoing. One of the main predictive factor for response to immune checkpoint inhibitors is PD-L1 expression status and this can change over time with the effect of therapies like chemotherapy and radiotherapy. The aim of this study is to determine whether PD-L1 expression status changes in recurrent gliomas after chemoradiotherapy and the impact of this change on survival.

Methods

PD-L1 expression of 29 patients was evaluated by an expert pathologist with immunohistochemistry. PD-L1 positivity was defined as expression in ≥ 1% of tumor cells. Change in PD-L1 expression status was defined as an absolute 5% difference between two resections.

Results

Of the 29 patients, 15 patients (51.7%) had PD-L1 expression in ≥ 1% of tumor cells and 7 patients (24.1%) had PD-L1 expression in ≥ 10% of tumor cells at diagnosis. Median survival of patients with baseline PD-L1

Conclusions

The PD-L1expression status changes in more than 40% of high grade glial tumors at recurrence after receiving chemotherapy and radiotherapy. So immune responsiveness of glial tumors can be modified by treatments. As the patients in this study did not receive immunotherapy after recurrence, the change in PD-L1 expression probably did not affect survival.

Clinical trial identification

Legal entity responsible for the study

Basak Oyan, Seyma Eren, Ozlem Sonmez

Funding

Yeditepe University Hospital

Disclosure

All authors have declared no conflicts of interest.