Efficacy and Safety of Ultra-Low-Dose Immunotherapy in Relapsed Refractory Solid Tumors: Phase III Superiority Randomized Trial (DELII)

PURPOSE Immune checkpoint inhibitors (ICIs) achieve sufficient receptor occupancy at much lower than standard approved doses. We hypothesized that ultra-low-dose nivolumab would retain clinical efficacy. PATIENTS AND METHODS In this phase III randomized superiority trial, patients with advanced solid tumors (Eastern Cooperative Oncology Group 0-1) and progression on ≥1 prior line of systemic therapy were randomly assigned 1:1 to ultra-low-dose nivolumab (20 mg intravenously once every 2 weeks) or standard chemotherapy (docetaxel or paclitaxel, as per tumor type). Treatment continued until progression or intolerable toxicity. The primary end point was overall survival (OS). RESULTS From June 2020 to February 2024, we enrolled 500 patients: 250 per arm; 52% had head and neck and 36% lung cancers. The median number of prior lines of therapy was 1 (range, 1-8); 29% had received ≥2 prior lines. Median OS was significantly longer with ultra-low-dose nivolumab: 5.88 months (95% CI, 4.99 to 7.13) versus 4.70 months (95% CI, 3.91 to 5.65; hazard ratio [HR], 0.80 [95% CI, 0.66 to 0.97]; P = .022). One-year OS was 27.3% versus 16.9%. Median progression-free survival was similar: 2.04 months (95% CI, 2.00 to 2.10) with ultra-low-dose nivolumab and 2.09 months (95% CI, 2.04 to 2.17) with chemotherapy (HR, 1.03 [95% CI, 0.86 to 1.23]; P = .77). Grade ≥3 treatment-related adverse events were less frequent with ultra-low-dose nivolumab (42.5% v 60.8%; P < .001). Quality of life (QoL) was significantly better with ultra-low-dose nivolumab. CONCLUSION Ultra-low-dose nivolumab significantly improves OS versus chemotherapy in pretreated solid tumors, with fewer severe toxicities and better QoL. These findings support re-evaluation of ICI dosing strategies and may enhance global access.