The cessation of anti-PD-1 antibodies of complete responders in metastatic melanoma.

The optimal duration of PD-1 antibodies for metastatic melanoma is unknown. In previous trials, there has been the potential to cease therapy if the patient achieves a complete response (CR). We aimed to assess the outcomes of patients who had ceased anti-PD-1 antibodies in this setting. A retrospective review was carried out of CR to PD-1-based therapy across two institutions. Patients were from the Pembrolizumab Named Patient Program (PEM NPP), Nivolumab monotherapy (NIVO), and reimbursed Pembrolizumab (r PEM). Patients had to have experienced a CR to PD-1-based therapy and ceased therapy because of this. Disease recurrence was the primary outcome measured. Twenty-nine patients (PEM NPP, N=20; Nivo, N=3; r PEM, N=6) ceased anti-PD-1 therapy after CR for observation. The median age was 64 (27-83) years. All patients had treatment discontinued for observation. The median time to CR was 10.5 months in the PEM NPP, 7.5 months on r PEM groups, and 17 months in the NIVO group. The median time off therapy in PEM NPP was 10 months, NIVO was 9 months, and r PEM was 4.5 months. To date, three patients have shown a relapse at a median follow-up off treatment of 8 months. This is the first report of patients who have intentionally ceased PD-1-based therapy because of CR. With a follow-up of 8 months off treatment, the risk of relapse was low. Data such as these are clinically relevant as we need to be able to discuss cessation of therapy and relevant from a pharmacoeconomic perspective, given the cost of PD-1 antibodies to society.