<scp>PD</scp> ‐L1 expression in melanoma shows marked heterogeneity within and between patients: implications for anti‐ <scp>PD</scp> ‐1/ <scp>PD</scp> ‐ <scp>L</scp> 1 clinical trials

Abstract

Summary This study evaluated the expression of PD ‐ L 1 in immunotherapy‐naïve metastatic melanoma patients to determine longitudinal intrapatient concordance and correlate PD ‐ L 1 status with clinicopathologic characteristics and outcome. PD ‐ L 1 expression was assessed by immunohistochemistry in 58 patients (43 primary tumors, 96 metastases). Seventy‐two percent of patients had at least one specimen expressing PD ‐ L 1 in ≥1% of tumor cells. Median positive tumor cell count overall was low (8% in nonzero specimens). PD ‐ L 1 expression was frequently discordant between primary tumors and metastases and between intrapatient metastases, such that 23/46 longitudinal patient specimens were discordant. PD ‐ L 1 was associated with higher TIL grade but not with other known prognostic features. There was a positive univariate association between PD ‐ L 1 expression in locoregional metastases and melanoma‐specific survival, but the effect was not observed for primary melanoma. In locoregional lymph node metastasis, PD ‐ L 1+/ TIL + patients had the best outcome, and PD ‐ L 1+/ TIL − patients had poor outcome.

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Affiliated Institutions

• Merck & Co., Inc., Rahway, NJ, USA (United States) US
• Royal Prince Alfred Hospital AU
• The University of Sydney AU
• Melanoma Institute Australia AU

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