CD274 and basaloid carcinoma: After adjusting for CTC presence, number of previous systemic treatment lines, and histological type (squamous cell/basaloid carcinoma vs others), higher PD-L1+ sEV concentration remained associated with worse OS (HR = 1.15, 95% CI 1.04–1.28, P = 0.008), like CTC presence, systemic treatment lines and squamous cell/basaloid carcinoma histology (Supplementary Table 6).