LAUSR

Patients with relapsed/refractory Hodgkin lymphoma (R/R HL) experience high response rates upon anti-PD1 therapy. In these patients, there is limited data about the optimal duration of treatment and the risk of relapse after anti-PD1 discontinuation. We have previously reported the outcome of 11 patients with R/R HL who discontinued anti-PD1 therapy after achieving a complete response (CR) upon nivolumab. These patients experienced a favorable outcome as only two of them had relapsed after a median follow-up of 21.2 months from discontinuation. Despite the low relapse rate observed in that study, physicians may be worried about the possibility to further rescue these heavily pretreated patients in case of relapse after anti-PD1 discontinuation. Notably, it is still unknown whether these patients will remain sensitive to a second course of antiPD1. Here, we investigated the efficacy of anti-PD1 retreatment in patients that were initially sensitive to anti-PD1 therapy but who relapsed after anti-PD1 discontinuation. We retrospectively analyzed patients with R/R HL who experienced a partial (PR) or CR upon anti-PD1 monotherapy and discontinued the treatment either because of unacceptable toxicity or due to prolonged remission, based on the physician’s decision. Patients who discontinued anti-PD1 therapy because of relapse/progression or underwent consolidation with allogenic stem cell transplantation (alloSCT) were not included. Patients meeting the eligibility criteria were identified through the French lymphoma network (LYSA). We identified seven patients who met the inclusion criteria. Their characteristics are summarized in Table 1. At anti-PD1 initiation, most patients presented with advanced disease (five of them had Ann Arbor stage III/IV) and had been heavily pre-treated (median number of prior systemic lines =6, seven had received prior brentuximab vedotin, five prior autologous stem cell transplantation (SCT) and two prior allogenic SCT). Overall, anti-PD1 was discontinued after a median duration of 11.4 months (range: 0–26.7) and a median of 23 infusions (range: 1–51). Anti-PD1 was discontinued because of prolonged remission (n=5) or toxicity (n=2, patient 5 had experienced grade 4 acute liver graft-versus-host-disease [aGvHD] and patient 7 grade 3 laryngeal tightness). The disease status at anti-PD1 discontinuation was CR for six patients and PR for one patient. The median time to relapse after anti-PD1 discontinuation was 12.1 months (range: 5.3–26.7). All patients were re-treated with the same anti-PD1 antibody as initially administered (six with nivolumab and one with pembrolizumab). All patients responded to anti-PD1 re-treatment (Figure 1). The best response was CR for four patients and PR for three patients. At the time of analysis (median follow-up of 19.2 months from anti-PD1 re-treatment), 4 of 7 patients have ongoing responses to antiPD1 monotherapy, three of them beyond 12 months. Interestingly, three patients discontinued anti-PD1 treatment after achieving a second objective response upon anti-PD1 re-treatment (patients 3, 5 and 7). Patient 3 discontinued anti-PD1 treatment a second time due to hyper-eosinophilia and then relapsed 2 months later. Patient 7 tolerated the second course of nivolumab well (notably, there was no recurrence of laryngeal tightness), achieved a PR and discontinued the treatment after 12 months. Unfortunately, he relapsed 5 months later. The patient then received a third course of nivolumab and achieved another PR which is still ongoing at 18 months. Patient 5 had undergone alloSCT prior to anti-PD1 therapy. He discontinued nivolumab after a single infusion due to grade 4 liver GvHD. Nevertheless, he achieved a CR which lasted 9 months. At relapse, he