Real-world outcomes of immune checkpoint inhibitor rechallenge in patients with classical Hodgkin lymphoma

Abstract

Abstract Background: Immune checkpoint inhibitors (ICIs) have been established as standard of care for patients with classical Hodgkin lymphoma (cHL), including relapsed or refractory (r/r) disease. However, ICIs discontinued in some patients due to treatment-related toxicities or disease progression may later be re-initiated. The outcomes of this common clinical practice of ICI re-initiation, or ‘rechallenge,‘ have not been evaluated. Here, we present real-world efficacy and safety data of ICI rechallenge in patients with cHL. Methods: We conducted a retrospective cohort study of patients with cHL treated with ICIs between 2015 and 2024 at Mayo Clinic sites. Patients were identified via institutional records using diagnostic and treatment codes. Included patients were adults ≥18 years with histologically confirmed diagnosis of cHL receiving ≥1 cycle of ICI therapy. Patients in the rechallenge cohort received a second course of ICI therapy following discontinuation of the initial ICI for any reason. The control cohort included patients with ICI discontinuation without subsequent rechallenge. Primary outcomes included progression-free survival (PFS), event-free survival (EFS), and duration of response (DOR), defined respectively as time from first ICI initiation to disease progression, time from first ICI initiation to disease progression, adverse events, treatment change, or death, and time from first recorded response per positron emission tomography–computed tomography until the occurrence of disease progression. Secondary outcomes included overall survival (OS), and incidence and severity of irAEs following ICI rechallenge. Survival outcomes were compared using propensity-score-matched (PSM) cohorts with a proportional Cox model. Results: A total of 145 patients were included. Of these, 30 (21%) underwent ICI rechallenge, while 115 (79%) received no subsequent ICI treatments. The median age was 40 years (interquartile range [IQR] 26-66). Most were male (59%), predominantly nodular sclerosis subtype (71%), Ann Arbor stage III-IV disease (65%), and ECOG ≤ 1 (96%). ICIs were utilized for r/r disease in 66%, with median 6 (IQR 4-13) cycles and follow up of 40.8 months (IQR 21.1–78.1). Patients received median 1 prior line of therapy (IQR 0-2.5). During initial ICI treatment, 34/145 patients (23%) experienced irAEs, including 17 patients (57%) in the rechallenge group and 17 (15%) in the non-rechallenge group. Most irAEs were of grade 1–2 severity, though 10 (30%) experienced grades ≥3 irAEs. irAE severity did not differ between groups. Among patients who underwent ICI rechallenge, the majority (53%) discontinued due to irAEs. The decision to pursue ICI rechallenge was driven predominantly by disease progression (63%). Among the 1:1 PSM cohorts using bone marrow transplant status and the International Prognostic Score, PFS did not significantly differ between rechallenged vs. non-rechallenged groups (HR 1.7, 95% CI 0.60–4.5, p=0.32). Similarly, no difference was noted among the groups in EFS and DOR using 1:3 PSM cohorts using the number of ICI cycles (HR 1.6, 95% CI 0.83–3.0, p = 0.16 and HR 1.6, 95% CI 0.37–7.0, p = 0.53, respectively). In the 1:1 matched cohort, ICI rechallenge was not associated with inferior OS compared to those without rechallenge (HR 1.6, 95% CI 0.48–5.4, p=0.43). irAE occurred in 20%, including pneumonitis (n=2), hepatitis (n=1), and pancreatitis (n = 1). Of the patients who had experienced irAEs during their initial ICI course, only two developed recurrent irAEs of the same type upon rechallenge, both at reduced severity. Overall, 80% of rechallenged patients did not experience any irAE with their second ICI course. Conclusions: ICI rechallenge was not associated with inferior PFS, EFS, DOR or OS compared patients without rechallenge. Among patients receiving ICI rechallenge after irAE, recurrence of same irAE was rare. ICI rechallenge may be a feasible and potentially effective strategy in selected patients with cHL.