title: Correlation of PD-L1 Expression of Tumor Cells with Survival Outcomes after Radical Intensity-Modulated Radiation Therapy for Non-Metastatic Nasopharyngeal Carcinoma.
abstract: OBJECTIVE
  We investigated if programmed death-ligand 1 (PD-L1) expression levels were prognostic of survival outcomes after intensity-modulated radiation therapy (IMRT) for non-metastatic nasopharyngeal carcinoma (NPC).
  
  
  METHODS
  104 patients with non-metastatic NPC treated with radical IMRT were investigated for their PD-L1 expression by immunohistochemistry (IHC) which were correlated with survival endpoints including locoregional failure-free survival (LRFFS), progression-free survival (PFS), distant metastasis-free survival (DMFS) and overall survival (OS).
  
  
  RESULTS
  After a median follow-up of 7.6 years, 21 (20.2%), 19 (18.3%) and 31 (29.8%) patients suffered from locoregional failure, distant metastases and overall disease progression, respectively, and 31 (29.8%) patients died. Patients whose tumors had PD-L1 IHC 2+ (moderate to strong membrane staining in ≥ 25% of tumor cells) enjoyed longer LRFFS (5-year 100% vs. 74.4%, Hazard ratio [HR], 0.159, 95% confidence interval [CI], 0.021-0.988; P = 0.042) and marginally longer PFS (5-year 95.0% vs. 65.2%, HR, 0.351, 95% CI, 0.08-0.999, P = 0.067) compared to those whose tumors had PD-L1 IHC 0 (minimal membrane staining with PD-L1 in < 5% tumor cells or no staining with PD-L1) or 1+ (minimal to moderate membrane staining with PD-L1 in between 5-24% tumor cells). PD-L1 IHC 2+ was independently prognostic of both LRFFS (P = 0.014) and PFS (P = 0.045) in multivariable analyses. Only induction chemotherapy followed by concurrent chemoradiation was prognostic of DMFS (P = 0.003) and no prognostic factor for OS was identified.
  
  
  CONCLUSIONS
  PD-L1 expression levels correlated with LRRFS and PFS in non-metastatic NPC treated with radical IMRT. It may play a role in radiosensitivity for NPC, which should be further confirmed in prospective studies using immunotherapy together with IMRT.
authors.affiliation: Department of Clinical Oncology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong.
authors.forename: Victor H F
authors.initials: VH
authors.lastname: Lee
authors.affiliation: Anatomical Pathology, Queen Mary Hospital, Hong Kong, Hong Kong.
authors.forename: Anthony W I
authors.initials: AW
authors.lastname: Lo
authors.affiliation: Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong.
authors.forename: Chun-Yin
authors.initials: CY
authors.lastname: Leung
authors.affiliation: Anatomical Pathology, Queen Mary Hospital, Hong Kong, Hong Kong.
authors.forename: Wai-Hung
authors.initials: WH
authors.lastname: Shek
authors.affiliation: Department of Clinical Oncology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong.
authors.forename: Dora L W
authors.initials: DL
authors.lastname: Kwong
authors.affiliation: Department of Clinical Oncology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong.
authors.forename: Ka-On
authors.initials: KO
authors.lastname: Lam
authors.affiliation: Department of Clinical Oncology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong.
authors.forename: Chi-Chung
authors.initials: CC
authors.lastname: Tong
authors.affiliation: Department of Clinical Oncology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong.
authors.forename: Chun-Kin
authors.initials: CK
authors.lastname: Sze
authors.affiliation: Department of Clinical Oncology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong.
authors.forename: To-Wai
authors.initials: TW
authors.lastname: Leung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D060890:B7-H1 Antigen / Q000235:genetics / Q000378:metabolism*; D002277:Carcinoma / Q000175:diagnosis / Q000378:metabolism* / Q000401:mortality* / Q000532:radiotherapy; D003131:Combined Modality Therapy; D005260:Female; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000175:diagnosis / Q000378:metabolism* / Q000401:mortality* / Q000532:radiotherapy; D009367:Neoplasm Staging; D011379:Prognosis; D012372:ROC Curve; D050397:Radiotherapy, Intensity-Modulated; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D060890:B7-H1 Antigen