Data on adverse drug reactions (ADRs) of immune checkpoint inhibitors (ICIs) used in oncology are mainly derived from clinical trials or cancer-specific reviews. We aim to analyze ADRs that occurred in patients treated with ICIs in real life.

We conducted an observational study on a historical cohort of the University Hospitals of Lyon. All patients who initiated an ICI treatment for any cancer in 2017 were included. Patients were followed from the first infusion until 90 days after the last one, death, date of last news or end of the study period (28 February 2019), whichever came first. Two pharmacovigilance specialists assessed the accountability and the severity of each ADR using Naranjo algorithm and common terminology criteria for adverse events (CTCAE) classification, respectively.

248 patients were included. They were treated with anti-PD-(L)-1, mainly nivolumab (70.6%) and pembrolizumab (25.8%). Lung cancer (62.1%) and melanoma (20.2%) were the most represented cancers. 139 ADRs occurred in 93 patients (37.5%), on average at the 6^th cure (±6.8). ADRs mainly concerned skin (29.5%), endocrine (19.4%) and digestive (10.8%) systems. 17.3% of ADRs were grades III-V and two patients died because of ADRs. By comparing patients with (N=93) or without (N=155) ADRs, all characteristics appeared similar except for age, number of infusions received and death status. The spontaneous notification rate found in this study was 5.8% for all grade ADRs (N = 8) but raised to 23.8% when only grades higher than III were considered (N = 5).

Our results are consistent with literature data in frequency and type of serious ADRs. We found a lower frequency of ADRs of any grade, which could be explained by a fairer causality assessment in our study than in clinical trials.