PD‐L1 expression in vulvar cancer: a systematic review and meta‐analysis

Programmed cell death ligand‐1 (PD‐L1) expression in cancer may predict clinical response to immunotherapeutic treatment with PD‐1/PD‐L1 inhibitors. Within the vulvar cancer field, PD‐L1 expression has only been assessed by a few studies. We conducted a meta‐analysis to examine the prevalence of PD‐L1 positivity in vulvar cancer. PubMed, Embase, and Cochrane were searched for articles reporting on PD‐L1 expression in vulvar cancer. Study selection and data extraction were performed independently by two authors. We extracted data on PD‐L1 prevalence in vulvar cancer according to combined positive score (CPS) and tumour proportion score (TPS). Cutoff values for positivity were ≥1 or ≥10 for CPS and ≥1% and ≥5% for TPS. Random‐effects models were used to estimate pooled PD‐L1 prevalence, with 95% confidence intervals (CIs). Tests of between‐study heterogeneity were evaluated by the I2 statistics. Sources of heterogeneity were explored by subgroup analyses and meta‐regression. In total, 19 studies were included. Pooled PD‐L1 prevalence in vulvar cancer was 83.4% (95% CI: 70.8–91.3; I2 = 80.0) and 53.9% (95% CI: 37.4–69.6; I2 = 93.0) according to CPS and TPS, respectively. Based on TPS, human papillomavirus (HPV)‐associated vulvar squamous cell carcinomas (SCC) showed a lower PD‐L1 prevalence (39.9%; 95% CI: 13.3–74.2) compared with HPV‐independent SCC (62.6%; 95% CI: 33.7–84.6), but meta‐regression showed no significant variation in PD‐L1 prevalence by HPV status. PD‐L1 prevalence was similar in advanced (44.9%; 95% CI: 29.8–61.1) and localized vulvar cancer (56.7%; 95% CI: 18.9–76.7). In conclusion, PD‐L1 expression in vulvar cancer is frequent but between‐study heterogeneity was high. Based on a subgroup of heterogenous studies, we found no strong variation in PD‐L1 prevalence according to HPV status and stage. Pooled data from 19 studies showed that PD‐L1 expression in vulvar cancer is frequent but between‐study heterogeneity was high. Subgroup analysis did not show strong variation in PD‐L1 prevalence according to HPV status and stage of disease.