2.4. Quality Assessment and Statistical Analyses

The methodological quality of the studies was assessed using the Newcastle–Ottawa scale, which consists of three factors: patient selection, comparability of the study groups, and assessment of outcomes. A score of 0–9 (allocated as stars) was assigned to each study. All meta-analyses were performed using STATASE 12.0. The HR was used to compare variables. All results were presented with 95% confidence intervals (CIs).

Statistical heterogeneity between different studies was assessed using the chi-square test, with the level of significance set at p < 0.10. Heterogeneity was quantified using the I² statistic. Heterogeneity was considered substantial when I² was >50%. A random-effects model was used for data analysis due to the moderate heterogeneity between different studies.

Subgroup analyses were performed to investigate the effect of early dermatological irAEs on anti-PD-1/PD-L1 efficacy. Potential publication bias was assessed using visual inspection of a funnel plot and was evaluated using Begg’s regression asymmetry tests. A p-value <0.05 was considered statistically significant.