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

The randomised phase 3 DELII trial, published in the Journal of Clinical Oncology (April 2026), evaluated an ultra-low-dose immunotherapy regimen in patients with relapsed or refractory solid tumours — a population with severely limited treatment options. The trial used a superiority design and showed an advantage over the control arm with substantially reduced doses of immune checkpoint inhibitors. If the result is confirmed, lower dosing could mean less toxicity and lower cost, which matters most where access to immunotherapy is constrained. It is one of the first large attempts to validate the ultra-low-dose concept across a heterogeneous population of advanced solid tumours.