medwireNews: Exploratory analysis from the PACIFIC trial sheds light on the impact of PD-L1 tumor cell expression in stage III non-small-cell lung cancer (NSCLC) patients who received consolidation treatment with the PD-L1 inhibitor durvalumab after concurrent chemoradiation.
As reported in the Annals of Oncology, PD-L1 status was evaluable for 451 of the participants, the majority (67%) of whom had at least 1% tumor cell expression, while 32% of patients had expression of 1–24%, and 35% had expression of 25% or greater.
Using data up to the time of the trial’s primary analysis, median progression-free survival (PFS) was consistently significantly better with durvalumab than placebo regardless of whether patients had expression levels of 25% or more (17.8 vs 3.7 months, hazard ratio [HR]=0.41) or less than 25% (16.9 vs 6.9 months, HR=0.59).
A PFS survival benefit was also found for patients with at least 1% expression (17.8 vs 5.6 months, HR=0.46), but the difference did not reach significance for patients with less than 1% expression (10.7 vs 5.6 months, HR=0.73).
Durvalumab also improved overall survival (OS) for most PD-L1 expression subgroups with a significant HR of 0.50 for patients with expression of at least 25% and trends towards improved OS for those with levels less than 25%, 1–24% and 1% or above.
There was no indication of OS benefit for patients with PD-L1 expression below 1%, although researchers note this was based on “a small sample size with too few events, overlapping [confidence intervals], and inadvertent prognostic imbalances favouring the placebo group,” and suggest these factors “preclude robust conclusions regarding OS” in this subgroup.
Luis Paz-Ares (Hospital Universitario 12 de Octubre, Madrid, Spain) and co-authors therefore conclude that “prospectively planned studies to assess outcomes with immunotherapies in patients with different levels of tumour PD-L1 expression are warranted (e.g. the phase 3 PACIFIC-5 trial of durvalumab after concurrent or sequential [chemoradiotherapy] in patients with Stage III NSCLC).”
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