Circulating CD8 lymphocytes predict response to atezolizumab–bevacizumab in hepatocellular carcinoma

Abstract Due to the lack of biomarkers predictive of response to atezolizumab–bevacizumab, the standard of care for advanced HCC, we analyzed baseline and early on‐treatment variation of peripheral lymphocyte populations of 37 prospective patients treated by atezolizumab–bevacizumab and in 15 prospective patients treated by sorafenib or lenvatinib (TKIs). RNAseq analysis followed by RT‐PCR validation on patients‐derived PBMC was also performed. At first imaging, re‐evaluation 13 patients receiving atezolizumab–bevacizumab, showed an objective response, 17 stable disease, while 7 were nonresponders. Baseline CD8+ and CD8+PD‐L1+ peripheral lymphocytes were lower in responders versus nonresponders ( T ‐test, p = 0.012 and 0.004, respectively). At 3 weeks, 28 of 30 responders displayed a rise of CD8+PD1+ lymphocytes with a positive mean fold change of 4.35 (±5.6 SD), whereas 6 of 7 nonresponders displayed a negative fold change of 0.89 (±0.84 SD). These changes were not observed in patients treated by TKIs. TRIM56, TRIM16, TRIM64, and Ki67 mRNAs were validated as upregulated in responders versus nonresponders after 3 weeks after treatment start, providing possible evidence of immune activation. Baseline CD8+ and CD8+PD‐L1+ peripheral lymphocytes and early changes in CD8+PD1+ lymphocytes predict response to atezolizumab–bevacizumab providing noninvasive markers to complement clinical practice in the very early phases of treatment of HCC patients.