Abstract 88P
Background
The use and approval of immune checkpoint inhibitors (ICIs) for the treatment of non-small cell lung cancer (NSCLC) depends on PD-L1 expression in the tumor tissue. Nevertheless, PD-L1 often fails to predict response to treatment. One possible explanation could be a change of PD-L1 expression during the course of disease and the neglect of re-assessment. The purpose of this study was a longitudinal analysis of PD-L1 expression in patients with relapsed NSCLC.
Methods
We retrospectively analyzed PD-L1 expression in patients with early stage NSCLC and subsequent relapse in preoperative samples, matched surgical specimens and biopsy samples of disease recurrence. Ventana PD-L1 (SP263) immunohistochemistry assay was used for all samples. PD-L1 expression was scored based on clinically relevant groups (0%, 1-49%, ≥50%). The primary endpoint was the change of PD-L1 score-group between preoperative samples, matched surgical specimens and relapsed tumor tissue.
Results
We identified 395 consecutive patients with stage I-III NSCLC and 136 (34%) patients with a subsequent relapse. For 87 patients at least two specimens for comparison of PD-L1 expression between early stage and relapsed disease were available. In 72 cases a longitudinal analysis between preoperative biopsy, the surgically resected specimen and biopsy of disease recurrence was feasible. When comparing preoperative and matched surgical specimens, a treatment-relevant conversion of PD-L1 expression group was found in 25 patients (34.7%). Neoadjuvant treatment showed no significant effect on PD-L1 alteration (p=0.39). In 32 (36.8%) out of 87 cases a change of PD-L1 group was observed when biopsies of disease relapse were compared to early stage disease. Adjuvant treatment was not associated with a change in PD-L1 expression (p=0.16). Thirty-nine patients (54.2%) showed at least one change into a different PD-L1 score group during the course of disease. Fourteen patients (19.4%) changed the PD-L1 score group twice, five (6.9%) of them being found in all different score groups.
Conclusions
PD-L1 expression shows dynamic changes during course of disease. Consensus guidelines are needed for PD-L1 testing including time points of re-assessment, number of biopsies to be obtained and judgement of specimens.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.