Six-Dimensional Correction of Intra-Fractional Prostate Motion with CyberKnife Stereotactic Body Radiation Therapy

Abstract

Large fraction radiation therapy offers a shorter course of treatment and radiobiological advantages for prostate cancer treatment. The CyberKnife is an attractive technology for delivering large fraction doses based on the ability to deliver highly conformal radiation therapy to moving targets. In addition to intra-fractional translational motion (left–right, superior–inferior, and anterior–posterior), prostate rotation (pitch, roll, and yaw) can increase geographical miss risk. We describe our experience with six-dimensional (6D) intra-fraction prostate motion correction using CyberKnife stereotactic body radiation therapy (SBRT). Eighty-eight patients were treated by SBRT alone or with supplemental external radiation therapy. Trans-perineal placement of four gold fiducials within the prostate accommodated X-ray guided prostate localization and beam adjustment. Fiducial separation and non-overlapping positioning permitted the orthogonal imaging required for 6D tracking. Fiducial placement accuracy was assessed using the CyberKnife fiducial extraction algorithm. Acute toxicities were assessed using Common Toxicity Criteria v3. There were no Grade 3, or higher, complications and acute morbidity was minimal. Ninety-eight percent of patients completed treatment employing 6D prostate motion tracking with intra-fractional beam correction. Suboptimal fiducial placement limited treatment to 3D tracking in two patients. Our experience may guide others in performing 6D correction of prostate motion with CyberKnife SBRT.

Interfraction Anatomical Variability Can Lead to Significantly Increased Rectal Dose for Patients Undergoing Stereotactic Body Radiotherapy for Prostate Cancer

“…Several studies have been performed analyzing the intrafraction prostate motion during prostate SBRT. [20][21][22][23][24][25] These studies have all analyzed the time traces of the implanted fiducial markers and based on these data, planning margins and imaging frequency during treatment have been proposed. However, none of these studies have utilized volumetric imaging.…”

Dysuria Following Stereotactic Body Radiation Therapy for Prostate Cancer

“…Our institutional SBRT treatment planning and delivery has been previously described (17,26). Briefly, several days after placement of three to four gold markers, the patients underwent magnetic resonance (MR) and computed tomography (CT) imaging.…”

Improved Irritative Voiding Symptoms 3 Years After Stereotactic Body Radiation Therapy for Prostate Cancer

“…Stereotactic body radiation therapy treatment planning and delivery were conducted as previously described (23,24). Briefly, four to six stranded gold fiducials (1013-2-2, Best Medical International, Inc., Springfield, VA, USA) were placed into the prostate with two to three needle applicators via a transrectal or transperineal approach.…”