A Prospective Study of a Resorbable Intravesical Fiducial Marker for Bladder Cancer Radiation Therapy

Matthew D Greer; Stephanie K Schaub; Stephen R Bowen; Jay J Liao; Kenneth Russell; Jonathan J Chen; Emily S Weg; Juergen Meyer; Tristan Alving; George R Schade; John L Gore; Sarah P Psutka; Robert B Montgomery; Michael Schweizer; Evan Y Yu; Petros Grivas; Jonathan L Wright; Jing Zeng

doi:10.1016/j.adro.2021.100858

A Prospective Study of a Resorbable Intravesical Fiducial Marker for Bladder Cancer Radiation Therapy

Adv Radiat Oncol. 2021 Nov 21;7(2):100858. doi: 10.1016/j.adro.2021.100858. eCollection 2022 Mar-Apr.

Authors

Matthew D Greer¹, Stephanie K Schaub¹, Stephen R Bowen^{1

2}, Jay J Liao¹, Kenneth Russell¹, Jonathan J Chen¹, Emily S Weg¹, Juergen Meyer¹, Tristan Alving³, George R Schade³, John L Gore³, Sarah P Psutka³, Robert B Montgomery⁴, Michael Schweizer⁴, Evan Y Yu⁴, Petros Grivas⁴, Jonathan L Wright³, Jing Zeng¹

Affiliations

¹ Radiation Oncology and.
² Radiology, University of Washington, Seattle, Washington.
³ Department of Urology, University of Washington, Seattle, Washington.
⁴ Division of Medical Oncology, Department of Medicine, University of Washington, Fred Hutchinson Cancer Research Center, Seattle Cancer Care Alliance, Seattle, Washington.

Abstract

Purpose: We conducted a prospective pilot study to evaluate safety and feasibility of TraceIT, a resorbable radiopaque hydrogel, to improve image guidance for bladder cancer radiation therapy (RT).

Methods and materials: Patients with muscle invasive bladder cancer receiving definitive RT were eligible. TraceIT was injected intravesically around the tumor bed during maximal transurethral resection of bladder tumor. The primary endpoint was the difference between radiation treatment planning margin on daily cone beam computed tomography based on alignment to TraceIT versus standard-of-care pelvic bone anatomy. The Van Herk margin formula was used to determine the optimal planning target volume margin. TraceIT visibility, recurrence rates, and survival were estimated by Kaplan-Meier method. Toxicity was measured by Common Terminology Criteria for Adverse Events version 4.03.

Results: The trial was fully accrued and 15 patients were analyzed. TraceIT was injected in 4 sites/patient (range, 4-6). Overall, 94% (95% confidence interval [CI], 90%-98%) of injection sites were radiographically visible at RT initiation versus 71% (95% CI, 62%-81%) at RT completion. The median duration of radiographic visibility for injection sites was 106 days (95% CI, 104-113). Most patients were treated with a standard split-course approach with initial pelvic radiation fields, then midcourse repeat transurethral resection of bladder tumor followed by bladder tumor bed boost fields, and 14/15 received concurrent chemotherapy. Alignment to fiducials could allow for reduced planning target volume margins (0.67 vs 1.56 cm) for the initial phase of RT, but not for the boost (1.01 vs 0.96 cm). This allowed for improved target coverage (D_95% 80%-83% to 91%-94%) for 2 patients retrospectively planned with both volumetric-modulated arc therapy and 3-dimensional conformal RT. At median follow-up of 22 months, no acute or late complications attributable to TraceIT placement occurred. No patients required salvage cystectomy.

Conclusions: TraceIT intravesical fiducial placement is safe and feasible and may facilitate tumor bed delineation and targeting in patients undergoing RT for localized muscle invasive bladder cancer. Improved image guided treatment may facilitate strategies to improve local control and minimize toxicity.