The use of tissue fiducial markers in improving the accuracy of post-prostatectomy radiotherapy.

The aim of this retrospective study was to investigate the use of a radiopaque tissue fiducial marker (TFM) in the treatment of prostate cancer patients who undergo post-prostatectomy radiotherapy (PPRT). TFM safety, its role and benefit in quantifying the set-up uncertainties in patients undergoing PPRT image-guided radiotherapy were assessed.

A total of 45 consecutive PPRT patients underwent transperineal implantation of TFM at the level of vesicourethral anastomosis in the retrovesical tissue prior to intensity-modulated radiotherapy. Prostate bed motion was calculated by measuring the position of the TFM relative to the pelvic bony anatomy on daily cone-beam computed tomography. The stability and visibility of the TFM were assessed in the initial 10 patients.

No postoperative complications were recorded. A total of 3,500 images were analysed. The calculated prostate bed motion for bony landmark matching relative to TFM were 2.25 mm in the left-right, 5.89 mm in the superior-inferior, and 6.59 mm in the anterior-posterior directions. A significant 36% reduction in the mean volume of rectum receiving 70 Gy (rV70) was achieved for a uniform planning target volume (PTV) margin of 7 mm compared with the Australian and New Zealand Faculty of Radiation Oncology Genito-Urinary Group recommended PTV margin of 10 mm.

The use of TFM was safe and can potentially eliminate set-up errors associated with bony landmark matching, thereby allowing for tighter PTV margins and a consequent favourable reduction in dose delivered to the bladder and rectum, with potential improvements in toxicities.

Radiation oncology journal. 2019 Mar 31 [Epub]

Michael Chao, Huong Ho, Daryl Lim Joon, Yee Chan, Sandra Spencer, Michael Ng, Jason Wasiak, Nathan Lawrentschuk, Kevin McMillan, Shomik Sengupta, Alwin Tan, George Koufogiannis, Margaret Cokelek, Farshad Foroudi, Tristan-Scott Khong, Damien Bolton

The Austin Hospital, Heidelberg, Australia., Genesis Cancer Care Victoria, Melbourne, Australia., Box Hill Hospital, Box Hill, Australia., The Bays Hospital, Mornington, Australia., The Ringwood Private Hospital, Ringwood East, Australia.