An Interventional Radiology Method for In Situ Assessments of Cancer Drug Response: Preclinical Development, Feasibility, and Safety

Purpose To evaluate the technical feasibility and safety of a nonsurgical interventional method for placement and retrieval of implantable microdevices (IMDs) in a rabbit tumor model. Materials and Methods This prospective preclinical feasibility and safety study was conducted from March 2022 to October 2024. Interventional IMD placement and retrieval were performed in 12 rabbits with single hindlimb VX2 tumors. Four or five IMDs were placed per animal. Each IMD delivered microdose quantities of three drugs (doxorubicin, topotecan, sunitinib) into 18 spatially distinct microscopic tumor regions over 24-48 hours. An over-the-wire biopsy procedure was used to extract the IMDs and surrounding tumor. Technical success was defined per animal as retrieval of at least one tumor region containing each of the three drugs. Overall region-level retrieval success rate was calculated as the overall percentage of drug-exposed regions retrieved successfully. Safety was determined by monitoring animals for adverse events. Procedure durations were assessed to inform clinical translation. Statistical analysis included calculation of binomial 95% CIs for success rates and summary statistics (mean ± SD) for region yield and procedure times. Results Twelve rabbits received 52 IMDs (mean, 4.3 ± 0.5 per animal) generating 936 drug-exposure sites. Technical success was 100% (12 of 12; 95% CI: 73.5, 100). Mean per animal retrieval was 50.7 regions ± 11.4 (range, 33-69), with an overall region-level success rate of 65% (608 of 936; 95% CI: 62, 68). No Common Terminology Criteria for Adverse Events grade 2 (moderate) or higher adverse events were observed. In two animals, IMDs dislodged from the guidewire and were retained in the tumor; no symptoms developed, and no additional intervention was required (grade 1). Implantation procedure duration was 30.3 minutes ± 5.3 and retrieval procedure duration was 49.1 minutes ± 6.3. Conclusion Interventional IMD placement and retrieval in a rabbit soft tissue tumor model was technically feasible and safe. This approach demonstrated the capacity to recover multiple drug-exposed regions for in situ assessment of local drug effects. <b>Keywords:</b> Implantable Microdevice, Personalized Treatment, Percutaneous Biopsy, Phase 0 Trials, Microdosing, Interventional Radiology <i>Supplemental material is available for this article.</i> © RSNA, 2025.