Improving our knowledge in PD-L1 testing in lung cancer: the archival sample is ‘promoted’!
Authors: A. Morabito
Journal: Annals of Oncology (2018)

The therapeutic approach for the second-line treatment of patients with advanced non-small-cell lung cancer (NSCLC) without actionable mutations has been recently revolutionized by the approval of immune checkpoint inhibitors. Nivolumab, pembrolizumab and atezolizumab improved overall survival (OS) in patients with advanced pretreated NSCLC with both squamous and nonsquamous histology compared with single-agent docetaxel (Table 1) [1.Brahmer J. Reckamp K.L. Baas P. et al.Nivolumab versus docetaxel in advanced squamous-cell non-small-cell lung cancer.N Engl J Med. 2015; 373: 123-135Crossref PubMed Scopus (5889) Google Scholar, 2.Borghaei H. Paz-Ares L. Horn L. et al.Nivolumab versus docetaxel in advanced nonsquamous non-small-cell lung cancer.N Engl J Med. 2015; 373: 1627-1639Crossref PubMed Scopus (6326) Google Scholar, 3.Herbst R.S. Baas P. Kim D.-W. et al.Pembrolizumab versus docetaxel for previously treated, PD-L1-positive, advanced non-small-cell lung cancer (KEYNOTE-010): a randomised controlled trial.Lancet. 2016; 387: 1540-1550Abstract Full Text Full Text PDF PubMed Scopus (4242) Google Scholar, 4.Fehrenbacher L. Spira A. Ballinger M. et al.Atezolizumab versus docetaxel for patients with previously treated non-small-cell lung cancer (POPLAR): a multicentre, open-label, phase 2 randomised controlled trial.Lancet. 2016; 387: 1837-1846Abstract Full Text Full Text PDF PubMed Scopus (1855) Google Scholar, 5.Rittmeyer A. Barlesi F. Waterkamp D. et al.Atezolizumab versus docetaxel in patients with previously treated nonsmall-cell lung cancer (OAK): a phase 3, open-label, multicenter randomised controlled trial.Lancet. 2017; 389: 255-265Abstract Full Text Full Text PDF PubMed Scopus (2915) Google Scholar]. In the studies with nivolumab and atezolizumab, patients were not selected on the basis of programmed death ligand-1 (PD-L1) expression, on the contrary in the study with pembrolizumab (KEYNOTE-010), patients were included only if they were positive for PD-L1 expression [tumor proportion score (TPS) on at least 1% of tumor cells (TCs)] on the basis of a companion diagnostic test [PD-L1 immunohistochemistry (IHC) 22C3 pharmDx assay].Table 1Randomized clinical studies with immune checkpoint inhibitors in pretreated patients with advanced non-small-cell lung cancerStudyAuthorPhaseTreatmentPtsOR (%)PFS (months)OS (months)CheckMate 017Brahmer, 2015IIINivolumab versus docetaxel, (squamous)27220 versus 9, P = 0.0083.5 versus 2.8, P < 0.0019.2 versus 6.0, HR: 0.59, P < 0.001CheckMate 057Borghaei, 2015IIINivolumab versus docetaxel, (non-squamous)58219 versus 12, P = 0.022.3 versus 4.2, P = 0.3912.2 versus 9.4, HR: 0.73, P = 0.0015POPLARFehrenbacher, 2016IIAtezolizumab versus docetaxel28715 versus 152.7 versus 3.012.6 versus 9.7, HR: 0.73, P = 0.04OAKRittmeyer, 2017IIIAtezolizumab versus docetaxel85014 versus 132.8 versus 4.0, HR: 0.9513.8 versus 9.6, HR: 0.73, P = 0.0003KEYNOTE 010Herbst, 2016IIIPembrolizumab 2 versus pembrolizumab 10 versus docetaxel103418% (.0005) versus 18% (.00002) versus 9%3.9 (HR 0.88) versus 4.0 (HR 0.79) versus 4.010.4 (HR 0.71) versus 12.7 (HR 0.61) versus 8.5OR, objective response; PFS, progression-free survival; OS, overall survival; HR, hazard ratio; pts, patients. Open table in a new tab OR, objective response; PFS, progression-free survival; OS, overall survival; HR, hazard ratio; pts, patients. In this update of KEYNOTE-010 study, Herbst et al. [6.Herbst R.S. Baas P. Perez-Gracia J.L. et al.Use of archival versus newly collected tumor samples for assessing PD-L1 expression and overall survival: an updated analysis of KEYNOTE-010 trial.Ann Oncol. 2019; 30: 281-289Abstract Full Text Full Text PDF PubMed Scopus (67) Google Scholar] compared treatment response with pembrolizumab by PD-L1 expression in archival and newly collected tumor samples. The median time between sample collection and PD-L1 assessment was 250 days for archival samples and 11 days for new samples. The first finding of this analysis is that with a longer median follow-up (31 months), pembrolizumab continued to improve OS over docetaxel [hazard ratio (HR) 0.66; 95% confidence interval (CI) 0.57–0.77] in the intention-to-treat population. The second and most important finding of the study is that pembrolizumab led to an improvement in OS compared with docetaxel irrespective of tumor sample type (archival versus new collected), in both the TPS ≥ 50% and TPS ≥ 1% populations. In particular, for patients with TPS ≥50%, the OS HR for pembrolizumab versus docetaxel comparison was 0.64 (95% CI 0.45–0.91) and 0.40 (95% CI 0.28–0.56) for patients enrolled based on PD-L1 expression in archival samples and on newly collected tumor samples, respectively. For patients with TPS ≥1%, the OS HR was 0.74 (95% CI 0.59–0.93) and 0.59 (95% CI 0.48–0.73) for archival and newly collected tumor samples, respectively. The KEYNOTE-001 study has first demonstrated a clear association between PD-L1 tumor expression and antitumor efficacy of pembrolizumab in patients with metastatic NSCLC [7.Garon E.B. Rizvi N.A. Hui R. et al.Pembrolizumab for the treatment of non-small-cell lung cancer.N Engl J Med. 2015; 372: 2018-2028Crossref PubMed Scopus (4101) Google Scholar]. However, the comparability of the response to pembrolizumab in patients with archival and newly collected tumor samples by PD-L1 expression was not evaluated. Indeed, this is an important question, because previously collected archival tissue is often the most convenient and easily accessible tissue source for biomarker testing in the second-line setting. The results of this updated analysis of KEYNOTE-010 confirm that the PD-L1 test from the archival sample of the tumor can be used for evaluating the eligibility of patients to pembrolizumab treatment. These results are in agreement with those of the ATLANTIC study, a phase II study of durvalumab in patients with advanced heavily pretreated NSCLC [8.Midha A. Sharpe A. Scott M. et al.PD-L1 expression in advanced NSCLC: primary lesions versus metastatic sites and impact of sample age.J Clin Oncol. 2016; 34 (abstr 3025)Crossref Google Scholar]. In this study, both archival and recently acquired samples were available for 112 patients: concordance with recent samples was highest with archival samples less than 3 years old (76.2%). Of course, there are a number of key questions remaining to be addressed: which is the optimal IHC assay to assess PD-L1 expression? Are cytological materials adequate for PD-L1 assessment? What will be the role of pembrolizumab in the second-/third-line setting? What will be the role of PD-L1 in the next future? Different PD-L1 IHC assays have been developed for each PD-1/PD-L1 inhibitor, including 28-8 assay (Dako, Carpinteria, CA, USA) for nivolumab and SP142 assay (Ventana Medical Systems, Tucson, AZ, USA) for atezolizumab, approved both as complementary diagnostics tests and not required for the treatment, and 22C3 (Dako, Carpinteria, CA, USA) for pembrolizumab, approved as companion diagnostics test and required for the eligibility of patients [9.US Food and Drug Administration. Dako PD-L1 IHC 28-8 pharmDx. http://www.accessdata.fda.gov/cdrh_docs/pdf15/P150027c.pdf.Google Scholar, 10.US Food and Drug Administration. VENTANA PD-L1 (SP142) assay. https://www.accessdata.fda.gov/cdrh_docs/pdf16/P160006C.pdf.Google Scholar, 11.US Food and Drug Administration. Dako PD-L1 IHC 22C3 pharmDx. https://www.accessdata.fda.gov/cdrh_docs/pdf15/P150013c.pdf.Google Scholar]. Moreover, SP263 assay (Ventana Medical Systems, Tucson, AZ, USA) has been developed for durvalumab, recently approved for the treatment of patients with locally advanced NSCLC after completing chemo-radiotherapy and 73-10 assay (Dako, Carpinteria, CA, USA) was developed for avelumab [12.Antonia S.J. Kim S.-W. Spira A. et al.Safety and clinical activity of durvalumab (MEDI4736), an antiPD-L1 antibody, in treatment-näıve patients with advanced non–small-cell lung cancer.J Clin Oncol. 2016; 34 (abstr 9029)Crossref Google Scholar, 13.Antonia S.J. Villegas A. Vicente D. et al.Durvalumab after chemoradiotherapy in stage III non-small-cell lung cancer.N Engl J Med. 2017; 377: 1919-1929Crossref PubMed Scopus (2243) Google Scholar, 14.Gulley J.L. Rajan A. Spigel D.R. et al.Avelumab for patients with previously treated metastatic or recurrent non-small-cell lung cancer (JAVELIN Solid Tumor): dose-expansion cohort of a multicentre, open-label, phase 1b trial.Lancet Oncol. 2017; 18: 599-610Abstract Full Text Full Text PDF PubMed Scopus (219) Google Scholar]. The Blueprint project, a pivotal academic/professional society and industrial collaboration that assessed the feasibility of harmonizing the clinical use of these commercial PD-L1 IHC assays by using real life clinical lung cancer samples, showed highly comparable staining by the 22C3, 28-8 and SP263 assays to detect PD-L1 expression on TCs, less sensitivity with the SP142 assay and higher sensitivity with the 73-10 assay [15.Tsao M.S. Kerr K.M. Kockx M. et al.PD-L1 immunohistochemistry comparability study in real-life clinical samples: results of Blueprint Phase 2 Project.J Thorac Oncol. 2018; 13: 1302-1311Abstract Full Text Full Text PDF PubMed Scopus (422) Google Scholar]. Therefore, results from the Blueprint confirm the interchangeability among three different assays (22C3, 28-8 and SP263) for use in scoring expression of PD-L1 on TCs (on the basis of TPS). For the second question, a major issue for the clinical practice is that all PD-L1 tests have been developed and approved only for histologic samples, while 30%–40% of patients with metastatic lung cancer are still currently diagnosed only by cytological materials, through less invasive procedures. A high degree of agreement (85%–95%) on PD-L1 expression levels was recently observed between histologic and cytologic specimens in 86 paired Formalin-Fixed Paraffin-Embedded samples of cytologic cell block and histologic material from lung malignancies, using 28-8 and 22C3, suggesting that PD-L1 assessment on cytologic material is feasible and could be an alternative when histologic samples are not available [16.Skov B.G. Skov T. Paired comparison of PD-L1 expression on cytologic and histologic specimens from malignancies in the lung assessed with PD-L1 IHC 28-8 pharmDx and PD-L1 IHC 22C3 pharmDx.Appl Immunohistochem Mol Morphol. 2017; 25: 453-459Crossref PubMed Scopus (121) Google Scholar]. However, the technique should be standardized before recommended for clinical practice. The role of pembrolizumab in the second- or third-line therapy of advanced NSCLC patients will be likely decreasing in the next future, after the results of clinical trials demonstrating the efficacy of pembrolizumab in the first-line setting [17.Reck M. Rodríguez-Abreu D. Robinson A.G. et al.Pembrolizumab versus chemotherapy for PD-L1–positive non–small-cell lung cancer.N Engl J Med. 2016; 375: 1823-1833Crossref PubMed Scopus (5718) Google Scholar, 18.Gandhi L. Rodriguez-Abreu D. Gadgeel S. et al.Pembrolizumab plus chemotherapy in metastatic non-small-cell lung cancer.N Engl J Med. 2018; 378: 2078-2092Crossref PubMed Scopus (3096) Google Scholar, 19.Paz-Ares L. Luft A. Vicente D. et al.Pembrolizumab plus chemotherapy for squamous non-small-cell lung cancer.N Engl J Med. 2018; 379: 2040-2051Crossref PubMed Scopus (1742) Google Scholar]. In particular, the KEYNOTE-024 study showed that pembrolizumab significantly prolonged progression-free survival and OS compared with platinum-based chemotherapy as the first-line therapy of patients with advanced NSCLC and PD-L1 expression on at least 50% of TCs, reinforcing the importance of PD-L1 testing at diagnosis in all patients [17.Reck M. Rodríguez-Abreu D. Robinson A.G. et al.Pembrolizumab versus chemotherapy for PD-L1–positive non–small-cell lung cancer.N Engl J Med. 2016; 375: 1823-1833Crossref PubMed Scopus (5718) Google Scholar]. Following these results, we witnessed a major revolution in the diagnostic and therapeutic algorithm that now requires PD-L1 testing at diagnosis for all patients with any histology and the use of pembrolizumab in the first-line setting as single agent for patients with PD-L1 > 50% or in combination with chemotherapy for all the other patients eligible to the combination of immunotherapy and chemotherapy. Finally, PD-L1 is to date the only molecular factor able to guide the choice of an immunotherapy for patients with advanced NSCLC, but a number of PD-L1 testing limitations can confound its use as a predictive biomarker, including the heterogeneity and dynamics of PD-L1 expression, the absence of consensus regarding the relevance of geographic patterns of expression of PD-L1 or its expression on tumor or inflammatory cells within the tumor microenvironment. Therefore, a number of additional factors are under investigation, including the tumor mutation burden, tumor-infiltrating lymphocytes, and immune gene signatures that may identify tumors with preexisting immune activity and correlate with response to anti-PD-L1/PD-1 [20.Buttner R. Gosney J.R. Skov B.G. et al.Programmed death-ligand 1 immunohistochemistry testing: a review of analytical assays and clinical implementation in non–small-cell lung cancer.J Clin Oncol. 2017; 35: 3867-3877Crossref PubMed Scopus (271) Google Scholar]. In conclusion, the results of this updated analysis of KEYNOTE-010 confirm that PD-L1 expression is preserved following months of storage and suggest that re-biopsy in patients who have received prior anticancer treatment may not be required for clinical assessment of PD-L1 expression. Therefore, the evaluation of PD-L1 expression at baseline in addition, in the future, to genomic and immune profiles will help to define the best therapeutic strategy for each patient with advanced NSCLC. The Thoraco-Pulmonary Medical Oncology is supported by Associazione Italiana per la Ricerca sul Cancro (AIRC) (no grant number applies).