• Justin F Gainor, Alice T Shaw, Lecia V Sequist, Xiujun Fu, Christopher G Azzoli, Zofia Piotrowska, Tiffany G Huynh, Ling Zhao, Linnea Fulton, Katherine R Schultz, Emily Howe, Anna F Farago, Ryan J Sullivan, James R Stone, Subba Digumarthy, Teresa Moran, Aaron N Hata, Yukako Yagi, Beow Y Yeap, Jeffrey A Engelman, and Mari Mino-Kenudson.
• Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts. jgainor@partners.org mminokenudson@partners.org.
• Clin Cancer Res. 2016 Sep 15; 22 (18): 4585-93.

PurposePD-1 inhibitors are established agents in the management of non-small cell lung cancer (NSCLC); however, only a subset of patients derives clinical benefit. To determine the activity of PD-1/PD-L1 inhibitors within clinically relevant molecular subgroups, we retrospectively evaluated response patterns among EGFR-mutant, anaplastic lymphoma kinase (ALK)-positive, and EGFR wild-type/ALK-negative patients.Experimental DesignWe identified 58 patients treated with PD-1/PD-L1 inhibitors. Objective response rates (ORR) were assessed using RECIST v1.1. PD-L1 expression and CD8(+) tumor-infiltrating lymphocytes (TIL) were evaluated by IHC.ResultsObjective responses were observed in 1 of 28 (3.6%) EGFR-mutant or ALK-positive patients versus 7 of 30 (23.3%) EGFR wild-type and ALK-negative/unknown patients (P = 0.053). The ORR among never- or light- (≤10 pack years) smokers was 4.2% versus 20.6% among heavy smokers (P = 0.123). In an independent cohort of advanced EGFR-mutant (N = 68) and ALK-positive (N = 27) patients, PD-L1 expression was observed in 24%/16%/11% and 63%/47%/26% of pre-tyrosine kinase inhibitor (TKI) biopsies using cutoffs of ≥1%, ≥5%, and ≥50% tumor cell staining, respectively. Among EGFR-mutant patients with paired, pre- and post-TKI-resistant biopsies (N = 57), PD-L1 expression levels changed after resistance in 16 (28%) patients. Concurrent PD-L1 expression (≥5%) and high levels of CD8(+) TILs (grade ≥2) were observed in only 1 pretreatment (2.1%) and 5 resistant (11.6%) EGFR-mutant specimens and was not observed in any ALK-positive, pre- or post-TKI specimens.ConclusionsNSCLCs harboring EGFR mutations or ALK rearrangements are associated with low ORRs to PD-1/PD-L1 inhibitors. Low rates of concurrent PD-L1 expression and CD8(+) TILs within the tumor microenvironment may underlie these clinical observations. Clin Cancer Res; 22(18); 4585-93. ©2016 AACRSee related commentary by Gettinger and Politi, p. 4539.©2016 American Association for Cancer Research.

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