Gender representation in first and senior authorship of phase III solid-tumor trials presented at the ASCO Annual Meeting, 2015-2025.

9006 Background: Authorship in clinical trials reflects access to research infrastructure, funding, and academic advancement. While gender gaps have been described, longitudinal trends and structural correlates remain poorly characterized. We examined temporal trends and determinants of gender representation among first and senior authors of phase III solid-tumor trials presented at the ASCO Annual Meeting. Methods: We performed a cross-sectional analysis of all phase III solid-tumor trial abstracts presented at the ASCO Annual Meeting from 2015–2025. Data included year, tumor track (breast, gastrointestinal [GI], other), funding source (industry, academic, other), and first/senior authorship. Countries were classified by World Bank income group (high [HIC], upper-middle [UMIC], lower-middle [LMIC], low-income [LIC]) and global region (North America, Europe & Central Asia, East Asia & Pacific, other). Author gender was assigned using publicly available professional profiles and validated automated tools (≥90% certainty). Temporal trends were assessed using Cochran-Armitage tests. Multivariable logistic regression models evaluated factors associated with women authorship. Results: Across 1,517 abstracts (3,034 authorships), women comprised 845 authors (27.9%). Most trials were industry funded (63.7%), focused on GI malignancies (20.1%), and based in HIC (84.9%). Using first author as reference group, senior author had higher odds of being male in multivariable analysis (OR=1.30, p=0.001). Women had lower odds of senior authorship compared with first authorship (aOR 0.77, 95% CI 0.65–0.90). Female authorship increased over time (24.9% in 2015–2020 vs. 30.0% in 2021–2025, p =0.002; aOR 1.34, 95% CI 1.13–1.58), most pronounced among senior authors (aOR 1.55, 95% CI 1.21–1.99; p =0.006). Women authorship varied by tumor track, with lower odds in GI compared with breast trials (aOR 0.49, 95% CI 0.38-0.64). Compared with North America, East Asia and Pacific affiliation was associated with higher odds of women authorship overall (aOR 1.54, 95% CI 1.15–2.07), strongest among first authors (aOR 1.89, 95% CI 1.25–2.91). Among senior authors, LMIC affiliation was associated with lower odds of women authorship compared to HICs (aOR 0.11, 95% CI 0.01–0.56). Conclusions: In the largest global oncology conference, women authorship in phase III solid-tumor trials has improved over the past decade but remains uneven, with persistent gaps in senior authorship. Authorship role, era, and tumor track by gender. Characteristic Women (N=845, 27.9%) Men (N=2,182, 71.9%) P -value Authorship role 0.002 First author 462 (54.7) 1,055 (48.4) Senior author 383 (45.3) 1,127 (51.6) Era 0.002 2015–2020 310 (36.7) 934 (42.8) 2021–2025 535 (63.3) 1,248 (57.2) Tumor track <0.001 Breast 203 (24.0) 307 (14.1) Gastrointestinal 150 (17.8) 456 (20.9) Other solid tumors 492 (58.2) 1,419 (65.0)