Serum alanine aminotransferase as an early marker of outcomes in patients receiving anti-PD-1 or anti-CTLA-4 antibody

Immune-oncology (IO) drug therapy is effective against various types of cancer. Although several, potential, clinical predictive markers have been identified, none so far have proven reliable. Herein we evaluated changes in serum alanine aminotransferase (ALT), which is upregulated by the accumulation of activated CD8+T cells in the liver, as a potentially reliable predictive marker. We retrospectively analyzed 265 patients with advanced malignancies at three institutions between 2016 and 2019. The patients received IO drug therapy. We defined the ALT ratio (ALR) as the serum ALT value at baseline / the highest serum ALT during IO drug therapy, then determined whether the ALR correlated with the objective response rate or progression-free survival. The median follow-up was 3.1 months. We observed objective responses in 65 patients. The ALR ranged from 0.19 to 32.2 (median 1.5), and a significant ALR increase was observed in responders (p < 0.001). In receiver operating characteristic analysis, ALR = 1.55 had the highest sensitivity and specificity. The patients with ALR < 1.55 had a significantly poorer PFS than those with ALR ≥ 1.55. A high ALR was associated with a tumor response and good PFS in patients with advanced malignancies. The ALR based on activated cytotoxic T lymphocyte dynamics is therefore a reliable predictive marker.