Prospective Evaluation Fiducial Migration after Placement for Liver SBRT and Influence on Treatment Delivery

Abstract

Fiducial placement in liver tumors (HCC) for Robotic Radiosurgery (CK) treatment is critical. There is a possibility of migration and related issues. Present study evaluating the impact of fiducial migration after simulation and during treatment. Between Mar 2017-Mar 2018, 53 HCCs accrued in the ethical & scientific committee approved prospective study for CK treatment. Three fiducials were place in liver (CT/USG guided) for tracking. Fiducials placed by radiologist with ‘ideal’ fiducials will be equidistance from each other (max distance 5 cm, min distance 2 cm). CT scan imaging was done at immediate post-placement (D0), at Day-3 and Day-8 to evaluate migration. During treatment (Day-4-8) intra-fraction imaging done to track the fiducials position. Fifty three patients (Male 92%, mean age 60.2 yrs, ECOG 0-1 92%, Child-Pugh A 89%, B&C 11%, majority in seg II & VI, PVT disease 64%) with HCCs underwent fiducial placement under guidance (CT scan 69%). Among 159 fiducial placement, six (3.4%)[lung 2, spleen 1, Heart 1, abdomen 2] had displacement outside liver at immediate post-fiducial period (Day-0). Day-0 CT scan, min and max inter-fudicial distance, min & max distance from tumor, max & min inter-fiducial angle are 2.66 (0.819) & 4.8 (1.08) mm; 2.1 (0.7) & 5.12 (1.25) mm; 28.5 (11.8) & 83 (25.25) degree respectively. Maximum and minimum fiducial migration on Day 3 was 0.85 (0.22) and 028 (1.04) mm. Tracking range, co-linearity, tracking uncertainty on Day1-5 of treatment was 5.07, 4.5, 4.9, 5.1, 5.1; 27.02, 25.9, 27.2, 27.6, 27.8; 40.9, 44.3, 47.3, 49.7, 47.06 respectively. Maximum migration during treatment (Day 1-5) was 0.29, 0.27, 0.27, 0.28, and 0.31 respectively. Total migration after treatment (Day 8) from day 0 was 2.35 (0.271) mm. Migration score evaluated on Day 3 and Day 8 did not show any significant difference in fiducial position compared with day 0. Displacement of fiducials occurs at immediate post-fiducial period. There is no significant change in fiducial positions at Day-3 and Day 8 from baseline (D-0). Liver SBRT treatment after fiducial placement may be started immediate post-fiducial placement (Day 1). No additional advantage of waiting for 3 days or more for fiducial stabilization.