Systemic review of the robustness of randomized controlled trials for the treatment of cholangiocarcinoma in three domains: survival-inferred fragility index, restricted mean survival time, and the spin effect.

Background: The vast majority of patients with cholangiocarcinoma (CC) have advanced disease at diagnosis and are candidates for palliative treatment only. The robustness of the randomized controlled trials regarding the treatment of CC are assessed. Methods: A systematic review of all randomized control trials (RCT) of treatments for both intra- and extrahepatic CC between 2010 and 2020 was performed. The survival-inferred fragility index (SIFI; the minimum number of reassignments of the best survivors between arms that would overturn the statistical outcomes) was calculated. In addition, the gain, or loss, in survival in RCTs was evaluated by the restricted mean survival time (RMST) difference. Finally, the level of spin i.e., misrepresentation of study outcomes, was measured in inconclusive studies to assess distorted reporting strategies. Results: Out of 6,167 studies retrieved, 11 could be retained for full text revision (7 with both intra- and extrahepatic CC, 3 with peri-hilar CC, and 1 with peri-hilar or distal CC). Only 3 studies included resected patients (2 with both intra- and extrahepatic CC and 1 with peri-hilar or distal CC). Nine studies investigated systemic chemotherapy (including 3 after surgical resection), one study evaluated photodynamic therapy, and another investigated the use of an endoscopically inserted stent in the biliary tract. The median SIFI was -2 [interquartile range (IQR): -6.25, -0.25] across all studies. Overall, the median RMST difference was 0.56 months (IQR: 0.10, 0.95). Finally, for inconclusive studies, the level of spin was high, moderate, and low in respectively 12.5%, 25%, and 62.5% of the studies. Conclusions: RCTs of CC showed a low degree of robustness with a frequent proportion of associated spin.