Late immune-related adverse events in long-term responders to PD-1/PD-L1 checkpoint inhibitors: A multicentre study.

Background: Data on spectrum and grade of immune-related adverse events (irAEs) in long-term responders to immune checkpoint inhibitors (ICIs) are lacking.
Methods: We performed a retrospective multicenter study to characterized irAEs occurring after a 12-months minimum treatment period with PD-(L)1 ICIs in patients with advanced cancer. IrAEs were categorized into 'early' (≤12 months) and 'late' (>12 months).
Results: From September 2013 to October 2019, 436 consecutive patients were evaluated. Two hundred twenty-three experienced any grade early-irAEs (51.1%), whereas 132 experienced any grade late-irAEs (30.3%) (p < 0.0001). Among the latter, 29 (22%) experienced a recurrence of an early-irAEs, whereas 103 (78%) experienced de novo late-irAEs involving different system/organ. Among patients with late-irAEs, 21 experienced GIII/GIV irAEs (4.8%). Median time to onset of early-irAEs was 3.4 months (95% confidence interval [CI]: 2.8-4.2), whereas the median time to onset of late-irAEs was 16.6 months (95% CI: 15.8-17.6). Cumulative time-adjusted risk of disease progression according to both the early-irAEs (hazard ratio [HR] = 0.63 [95% CI: 0.30-1.29], p = 0.204) and late-irAEs occurrence revealed no statistically significant differences (HR = 0.75 [95% CI: 0.37-1.56], p = 0.452). In addition, the time-adjusted cumulative risk of death in accordance with both early-irAEs (HR = 0.79 [95% CI: 0.34-1.86], p = 0.598) and late-irAEs (HR = 0.92 [95% CI: 0.49-1.74], p = 0.811) did not show statistically significant differences.
Conclusion: Although less frequent than early-irAEs, late-irAEs are quite common in long responders to PD-(L)1 ICIs and are different in terms of spectrum and grade. Time-adjusted analysis revealed that the cumulative risk of disease progression and death were not significantly reduced in patients who experienced late-irAEs.
Competing Interests: Conflict of interest statement A.C. reports having received grants as speaker by MSD and Astra-Zeneca; grant consultancies by BMS, Roche, Novartis, Istituto Gentili and Ipsen. M.B. reports having received research funding by Roche, Pfizer, Seqirus, AstraZeneca, Bristol-Myers Squibb, Novartis and Sanofi; she also received honoraria for advisory role and as speaker at scientific events by Bristol-Myers Squibb, Novartis and Pfizer. M.R. reports having received honoraria for scientific events by Roche, Astrazeneca, Bristol-Myers Squibb, Merck Sharp & Dohme and Boehringer Ingelheim. R.G. reports to be a part of the advisory boards/Honoraria/Speakers’ fee/Consultant for: Astra Zeneca, Roche. All remaining authors declare no conflict of interest.
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