Abstract

Aim: This is a prospective study reporting on the safety and feasibility of an iodinated hydrogel tissue fiducial marker (IH TFM) for image guided radiation therapy in the treatment of muscle invasive bladder cancer.
Materials and Methods: From September 2015 to July 2017, four patients diagnosed with muscle invasive unifocal transitional cell carcinoma (TCC) bladder cancer were included in the study. Under general anaesthetic, patients underwent cystoscopic injection of IH into their tumour base. Patients subsequently underwent image guided RT. The total prescription was 64.0 - 66.0 Gy in 2.0Gy per fraction. Daily online cone-beam CT (CBCT) matching to IH TFM were performed throughout the course of radiation therapy (RT) to verify the extent of daily treatment shifts. IH volume, its stability and visibility were also evaluated.
Results: The volume of IH TFM remained consistent over the course of bladder radiotherapy. IH TFM match recorded the largest variations in the supero-inferior (SI) and antero-posterior (AP) directions with the largest geometrical shift of 5 mm was recorded. If bony landmark was used, a margin of up to 17.4 mm in the AP direction would be required to ensure adequate clinical target volume (CTV) coverage. In this study, we found IH TFM to be well tolerated and feasible, with no major adverse events noted as a result of injection.
Conclusion: This study demonstrates that IH TFM can be safely injected into the bladder mucosa and can be considered as a fiducial marker for bladder cancer.

Keywords

Bladder cancer, radiation therapy, iodinated hydrogel, tissue fiducial marker, bladder sparing