Association Of Pd-L1 Expression With Hotspot Mutations In Non-Small Cell Lung Cancer (Nsclc).

e21604 Background: PD-L1 is of great interest in many clinical trials on immunotherapy as a promising biomarker, however, its role in targeted therapy and correlation with hotspot mutations remains unclear. Methods: From May 6th 2019 to Jan 27th 2020, 609 NSCLC patients were prospectively enrolled. Targeted deep sequencing (~3000X) with a 605-gene panel was performed on tumor and blood sample from each patient. The expression of PD-L1 was tested by immunohistochemistry. PD-L1 expression level was defined as negative ( < 1%), low (1%~50%), and high (≥50%). Results: In the total 609 patients, the expression of PD-L1 was negative in 36.9% (n = 256), low in 51.7% (n = 315) and high in 11.3% (n = 69) of them. In 440 patients harboring hotspot mutations, 35.0% (n = 154) of them were identified as PD-L1 negative, 52.3% (n = 230) as PD-L1 low and 12.7% (56/440) as PD-L1 high. In 169 patients without hotspot mutations, there were 42.0% (71/169) of patients with negative PD-L1 expression, 50.3% (85/169) with low PD-L1 expression and 7.7% (13/169) with high PD-L1 expression. Mutation frequencies of several hotspot mutations were summarized in Table. Conclusions: This study showed that PD-L1 expression was associated with some hotspot mutations, such as BRAF_p.V600E, KRAS_p.G12/G13/Q61 and amplification of MET. Although the biological mechanism of this association is yet to be investigated, combination of hotspot mutations and PD-L1 expression could be a future direction in biomarker studies. [Table: see text]