Modeling positioning uncertainties of prostate cancer external beam radiation therapy using pre-treatment data

Abstract

Purpose To investigate the influence of treatment plan data and image guidance (IG) on positioning uncertainty during prostate cancer (PCa) radiotherapy (RT). Methods Body mass index (BMI), planning target volume (PTV), bladder volume (BV), and rectal cross section area (RCS) were collected for 267 consecutive PCa patients undergoing daily IGRT. Radiographic isocenter corrections to intra-prostatic fiducials for 12,490 treatment fractions were used to derive random (RE) and systematic (SE) inter-fraction uncertainties for the cardinal axes. These data were used to simulate RE and SE for weekly IG and Action Level (AL)-IG treatment protocols. Results SE and RE were 2–5 and 3–4 mm in the cardinal axes, respectively, during simulation of no IG. Without IG, positive correlations (p < 0.01) were noted for (1) anterior-posterior RE vs. RCS and BV and (2) cranio-caudal RE vs. RCS, BV and BMI. The RE increase was 3 mm for the highest quartile of RCS, BV and BMI. Daily IGRT eliminated this relationship. 3D IG corrections of 1 cm or more occured in 27% of treatment fractions and in 97% of patients. Conclusion PCa patients with elevated pre-treatment BV, RCS and BMI have increased inter-fractionation positioning uncertainty and appear the primary candidates for daily IGRT.

Residual positioning errors and uncertainties for pediatric craniospinal irradiation and the impact of image guidance

“…When investigating the isocenters individually, the positioning errors and uncertainties found in this study are comparable to previously published research for other sites [8,[13][14][15]. Al-Wassia et al [33] studied the effect of a 3-DoF couch correction, and found uncertainties Fig.…”

“…Setup uncertainties have been extensively studied in photon radiotherapy for various treatment sites [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Lately, proton radiotherapy has emerged as a prominent alternative to photon therapy for pediatric CSI and today, both treatment modalities are relevant when studying residual errors and uncertainties.…”

Image-guided radiotherapy reduces the risk of under-dosing high-risk prostate cancer extra-capsular disease and improves biochemical control

“…The patients’ planned dose distribution, CT data set and contours were extracted from the in-house treatment planning software and imported into the CERR software [ 21 ]. Using a programming script, the simulated isocenter position was sampled using a systematic and a random error using positioning uncertainty data from [ 22 ]. For IG-IMRT patients, however, the systematic error stems from lack of imaging isocentricity and misalignment vs. the radiation isocenter.…”

Stereotactic Body Radiation Therapy Treatment for Prostate Cancer: From Setup to Delivery Strategies

“…2 These uncertainties are mostly due to patient setup errors and extensive motion of the rectum and bladder that is dependent on organ filling. In this regard, an augmented impact of geometric uncertainties is expected when high doses per fractions are adopted.…”