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

A Phase III superiority randomized trial (DELII) published in the Journal of Clinical Oncology evaluated an ultra-low-dose immunotherapy regimen in patients with relapsed or refractory solid tumors, a population with severely limited treatment options. The study demonstrated that dramatically reduced doses of immunotherapy can achieve meaningful clinical benefit compared to control, potentially reshaping the risk-benefit calculus for heavily pretreated patients. If confirmed in practice, this dosing strategy could significantly lower treatment toxicity and cost while preserving efficacy, broadening global access to checkpoint inhibitor therapy. The findings, spanning 14 pages of JCO's April 2026 issue, represent one of the first large-scale validations of ultra-low-dose immune checkpoint approaches in a difficult-to-treat, heterogeneous solid tumor population.