Results of trials assessing transarterial chemoembolization for treating hepatocellular carcinoma are critically underreported

Objective: We aimed to evaluate to what extent the results of registered randomized controlled trials (RCTs) assessing transarterial chemoembolization (TACE) for treating hepatocellular carcinoma (HCC) are publicly available.

Methods: We searched the Cochrane Central Register of Controlled Trials, the International Clinical Trials Registry Platform, and primary registries for RCTs assessing TACE for treating HCC, registered between January 2008 and August 2018, that had exceeded their completion date by more than 1 year. We systematically searched PubMed, EMBASE, and Google Scholar for a publication as well as the registry for results. The main outcomes were the availability of results, and the time to the first availability of results (i.e., posted on the registry or published). Secondary outcomes were the proportion of results available at 12 and 36 months after completion.

Results: Among 67 identified RCTs, including a total target number to 11,599 participants, 26 had publicly available results (39%; i.e., 42% of total target number of participants). Results of 25 RCTs (37%) were published, with only 3 having results posted on the registry and 2 with both published and posted results. The median (Q1-Q3) time from completion to the first public availability of results was 18 months (11-29). The cumulative percentages of RCTs with results available were 10% (95% CI, 3-17%) and 29% (95% CI, 17-39%) at 12 and 36 months, respectively, after completion.

Conclusions: Despite the ethical commitments and societal expectations for disclosure of results, the availability of results of RCTs on TACE for treating HCC is very limited.

Key points: • Underreporting of trial results is a major cause of wasted medical research since inaccessible research results fail to help both patients and clinicians. • Transarterial chemoembolization (TACE) is the most common treatment for hepatocellular carcinoma (HCC) and has called for considerable research efforts. • Yet, almost two-thirds of randomized controlled trials assessing TACE for treating HCC did not yield any public results, either on the registry platform or in scientific journals.