LAUSR

PURPOSE Nivolumab, an anti-programmed death 1 antibody, produces antitumor effects by activating host immunity, which also causes immune-related adverse events (irAEs). The aim of this study was to analyze the association between antitumor effect and irAEs induced by nivolumab in patients with melanoma. METHODS Fifteen patients with melanoma who had received nivolumab at Tokushima University Hospital or Ehime University Hospital between January 2015 and December 2016 were enrolled in this study. Patients who had and did not have irAEs during nivolumab treatment were classified into an irAEs-positive group (n = 8) and an irAEs-negative group (n = 7), respectively. We compared the disease control rate (DCR) and overall survival (OS) between the 2 groups. Data on blood cell counts were also analyzed. FINDINGS After a median of 4 cycles of nivolumab treatment, irAEs occurred. The DCRs were 75% and 14% in the irAEs-positive and irAEs-negative groups, respectively (p < 0.05). OS in the irAEs-positive group was higher than that in the irAEs-negative group (p < 0.05). Multivariable Cox proportional hazards regression analysis revealed that irAE occurrence affected OS with nivolumab treatment. Moreover, the increase in baseline peripheral lymphocyte count at the time of onset of irAEs was significantly greater in the irAEs-positive group than in the irAEs-negative group after 4 cycles of nivolumab treatment (p < 0.05). IMPLICATIONS Our study indicated that clinical response with nivolumab treatment improves with irAE occurrence in patients with melanoma. Moreover, the early increase in peripheral lymphocyte count may act as a biomarker for predicting the occurrence of irAEs induced by nivolumab.