An Endorectal Balloon Reduces Intrafraction Prostate Motion During Radiotherapy

Journal Article · Fri Jun 01 04:00:00 EDT 2012 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/J.IJROBP.2011.07.028· OSTI ID:22056402

Louwe, Robert J.W. ^[1]; Langen, Katja M; Shah, Amish P; Kupelian, Patrick A ^[2]

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1. Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands)
2. Department of Radiation Oncology, M.D. Anderson Cancer Center Orlando, FL (United States)

Purpose: To investigate the effect of endorectal balloons (ERBs) on intrafraction and interfraction prostate motion during radiotherapy. Methods and Materials: Thirty patients were treated with intensity-modulated radiotherapy, to a total dose of 80 Gy in 40 fractions. In 15 patients, a daily-inserted air-filled ERB was applied. Prostate motion was tracked, in real-time, using an electromagnetic tracking system. Interfraction displacements, measured before each treatment, were quantified by calculating the systematic and random deviations of the center of mass of the implanted transponders. Intrafraction motion was analyzed in timeframes of 150 s, and displacements >1 mm, >3 mm, >5 mm, and >7 mm were determined in the anteroposterior, left-right, and superoinferior direction, and for the three-dimensional (3D) vector. Manual table corrections, made during treatment sessions, were retrospectively undone. Results: A total of 576 and 567 tracks have been analyzed in the no-ERB group and ERB group, respectively. Interfraction variation was not significantly different between both groups. After 600 s, 95% and 98% of the treatments were completed in the respective groups. Significantly fewer table corrections were performed during treatment fractions with ERB: 88 vs. 207 (p = 0.02). Intrafraction motion was significantly reduced with ERB. During the first 150 s, only negligible deviations were observed, but after 150 s, intrafraction deviations increased with time. This resulted in cumulative percentages of 3D-vector deviations >1 mm, >3 mm, >5 mm, and >7 mm that were 57.7%, 7.0%, 0.7%, and 0.3% in the ERB-group vs. 70.2%, 18.1%, 4.6%, and 1.4% in the no-ERB group after 600 s. The largest reductions in the ERB group were observed in the AP direction. These data suggest that a 5 mm CTV-to-PTV margin is sufficient to correct for intrafraction prostate movements when using an ERB. Conclusions: ERB significantly reduces intrafraction prostate motion, but not interfraction variation, and may in particular be beneficial for treatment sessions longer than 150 s.

• OSTI ID: 22056402
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 2 Vol. 83; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BALLOONS
CENTER-OF-MASS SYSTEM
MANUALS
PATIENTS
PROSTATE
RADIATION DOSES
RADIOTHERAPY
RANDOMNESS