The concepts of rechallenge and retreatment with immune checkpoint blockade in melanoma patients.

Forty to 60% of patients with advanced or metastatic melanoma respond to first-line immune checkpoint inhibitors (ICI) and half of all patients in the metastatic setting eventually progress. This review evaluated the latest long-term data from clinical trials. It also considered data from recent retrospective studies, as these address important questions for clinical practice. 'Retreatment' defined as 'repeated treatment with the same therapeutic class following relapse after adjuvant treatment has ended' and showed activity in selected patients with recurrence after regular completion of adjuvant PD-1 treatment. In melanoma patients with adjuvant PD-1 monotherapy who recur during adjuvant treatment, further treatment with PD-1 monotherapy seems to have no clinical utility, indicating the need for a therapy switch or escalation in these patients. Targeted therapy with BRAF/MEK inhibitors and ipilimumab-based therapy (alone or combined with PD-1 blockade) show clinical activity in patients who recur during and after adjuvant treatment. 'Rechallenge', defined as 'repeated treatment with the same therapeutic class following disease progression in patients who had clinical benefit with prior treatment for unresectable or metastatic disease', with pembrolizumab at progression in the advanced setting achieving additional disease control. If possible, 'escalation' (PD-1 inhibitors combined with additional agents) should be preferred to PD-1 inhibitor monotherapy rechallenge as higher response rates were demonstrated. The combination of PD-1 plus CTLA-4 was found to be more effective but not more toxic than CTLA-4 alone. Promising antitumor activity was observed for escalation to lenvatinib plus pembrolizumab, entinostat plus pembrolizumab, and relatlimab plus nivolumab. Retreatment, rechallenge and escalation are available options for patients with melanoma who relapse in the adjuvant or advanced setting.