The fragility index of randomized controlled trials in advanced/metastatic renal cell cancer.

Purpose: The fragility index (FI) has been applied as a supplement to the noncomprehensive P-values to assess the robustness of randomized controlled trials (RCTs). The objective of this study is to evaluate the statistical robustness of RCTs of advanced/metastatic renal cell cancer (a/mRCC) using the FI.

Materials and methods: RCTs related to a/mRCC published in the 4 highest-impact general medical journals and the 25 highest-impact urological journals between January 1, 2000, and December 31, 2023, were identified from PubMed database. The FI was calculated by using Fisher's exact test. Spearman's correlation analysis was conducted to assess potential correlates regarding FI.

Results: 16 eligible RCTs were screened with a median total sample size of 654.5 (IQR, 461-847) and a median patients lost to follow-up of 14 (IQR, 3-23). The median FI was 12.5 (IQR, 8.5-27), suggesting that a switch in outcomes in only 13 patients would have reversed the significance of the trials. The number of patients lost to follow-up exceeded or equaled to the FI in 7 (44%) RCTs. P-values were negatively associated with the FI, while the number of patients lost to follow-up and patients enrolled were not statistically significant.

Conclusion: Not all RCTs associated with a/mRCC are as statistically robust as previously considered and should therefore be construed carefully. We suggest that additional reporting of FI in urological RCTs as a supplement to the P-value to assist readers in concluding reliably by considering the fragility of the outcomes.