Abstract C065: Research biopsy participation and safety in cancer therapeutic trials

Abstract Background: Tumor biopsies are essential for biomarker discovery and validation of mechanism of action in early phase clinical trials, however, patients may be unwilling to participate. We examined biopsy safety and factors influencing biopsy participation in clinical trials. Methods: We analyzed active clinical trials that incorporated biopsies from at our Phase I program from January 1, 2023 to February 28, 2025. Patient demographics, disease characteristics and trial-specific factors were extracted from a prospectively maintained database. Biopsy characteristics were analyzed by mandatory or optional requirement status. Procedural-related complications were reported. Results: Among 91 trials, 60 (65.9%) were phase 1 studies and 80 (87.9%) were industry sponsored. Biopsy was required in 50 trials (54.9%), of which 10 permitted archival tissue. In 27 trials (29.7%) biopsy was optional, and in 13 trials (14.3%) both mandatory and optional biopsies were included. 648 patients were enrolled. Median age of patients was 61 years (IQR 51-69), and majority were female (n=346, 53.4%), white (n=491, 75.8%), and with in-state (Texas) location (n=331, 51.1%). The most common primary cancers were colorectal (n=121, 18.7%), pancreatic (n=103, 15.9%), and breast (n=79, 12.2%) cancers. Of 203 patients treated in cohorts requiring biopsy, 142 (70%) underwent biopsy. Of 216 patients treated in cohorts with optional biopsy requirement, 58 (26.9%) underwent biopsy. Among patients enrolled in cohorts with optional biopsy requirement, there were no statistically significant differences in age (p=0.54), gender (p=0.88), race (p=0.75), ethnicity (p=0.31), or location (p=0.41) between patients who underwent biopsy compared to those who did not. Of 269 biopsies performed, 96 (35.7%) were CT-guided while 122 (45.4%) were ultrasound-guided. The most common biopsy sites were liver (n=68, 25.3%), muscle/soft tissue (n=58, 21.6%), lymph node (n=27, 10.0%), and lung (n=14, 5.2%). 158 (58.7%) patients underwent pre-treatment, and 52(19.3%) patients underwent on-treatment biopsies. Five patients experienced pneumothorax and 2 required chest tube placement; all recovered fully without sequelae. Median time from consent to treatment was 20 days (IQR 15-26), with no significant difference between biopsy and no-biopsy groups (21 vs 20 days, p=0.81). Among patients enrolled in optional biopsy cohorts, there was no difference in time from consent to treatment between those who underwent biopsy vs those who did not (21 vs 19 days, p=0.15). Conclusion: Approximately a quarter of patients participated in optional research biopsies, with no treatment delays and low complication rates. Participation did not significantly differ by demographic or clinical factors. Further work investigating barriers to research biopsy participation is needed. Enhancing clear communication, patient-centered informed consent, and streamlined logistical strategies may improve equitable participation and advance biomarker-driven research. Citation Format: Taiwo Adesoye, Michelle L. Elders, Hung Le, David Hong, Sheferaw Y. Belay, Jordi A. Rodon, Ecaterina E. Dumbrava, Aung Naing, Sarina A. Piha-Paul, Siqing Fu, Tin-Yun Tang, Apostolia M. Tsimberidou, Alda L. Tam, Ravi Murthy, Lorna H. McNeill, Funda Meric-Bernstam. Research biopsy participation and safety in cancer therapeutic trials [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr C065.