In contrast, the multivariate OS model showed a marked reduction of heterogeneity after inclusion of covariates (τ2 decreasing from 0.933 to approximately 0), and the overall regression was highly significant (QM = 75.67; P < 0.001).
For multivariate models (CSS–multi, OS–multi, DFS–multi), Begg’s tests were non-significant and trim-and-fill did not impute additional studies (all k 0 = 0); although Egger’s test yielded a nominally significant P value for DFS–multi (P = 0.008), the absence of imputed studies and the similarity between original and adjusted estimates suggest that any small-study effects are unlikely to materially bias the results.
In the OS univariate model, none of the covariates reached conventional statistical significance, although UICC stage showed a positive trend (β = 0.62; P = 0.142), which remained directionally consistent after CR2-robust variance correction (p_CR2 = 0.176).
Results from other subgroups were directionally consistent but did not reach statistical significance.