Purpose: Conflicts of interest (COIs) in medical research can introduce biases affecting research integrity. This study investigated the scale and disclosure of COIs among Japanese authors of cancer clinical trials.
Methods: Fifty-eight cancer randomized controlled trials from 2020, involving 226 Japanese authors, were systematically abstracted and analyzed. The financial relationships between these authors and pharmaceutical companies were examined using payment data from 56 companies for the years 2018-2019. COI statements were extracted from each publication, and COI declaration rates were calculated by comparing declared companies against those that reported payments. The analysis was conducted at both the author and article levels. For author-level analyses, the declaration rate was calculated per declaration rather than per author. For article-level analyses, payments were aggregated and attributed to their respective articles.
Results: Phase III trials comprised 82.8% (48/58) of the included studies. Of 226 authors, 202 (89.4%) were medical doctors and 208 (92.0%) received at least one payment. The median number of companies providing at least one payment per author was 9 (IQR, 4-12), with a median total payment of $19,183 US dollars (USD; IQR, $5,158-$62,534 USD). Among 280 unique disclosures from authors with payments, only 29 (10.4%) accurately reported COIs, whereas 80 (28.6%) reported no COIs. For 58 articles, only two (3.4%) accurately reported COIs, seven (12.1%) reported no COIs, and 49 (84.5%) partially disclosed COI information.
Conclusion: Japanese cancer clinical trial authors frequently received industry payments, yet their COI disclosures were often inadequate. This highlights the need for stricter guidelines and improved education on COI reporting in Japan.