Is a 3-mm intrafractional margin sufficient for daily image-guided intensity-modulated radiation therapy of prostate cancer?

Authors

Adam D. Melancon, University of Texas MD Anderson Cancer Center
Jennifer C. O'Daniel, University of Texas MD Anderson Cancer Center
Lifei Zhang, University of Texas MD Anderson Cancer Center
Rajat J. Kudchadker, University of Texas MD Anderson Cancer Center
Deborah A. Kuban, University of Texas MD Anderson Cancer Center
Andrew K. Lee, University of Texas MD Anderson Cancer Center
Rex M. Cheung, University of Texas MD Anderson Cancer Center
Renaud de Crevoisier, University of Texas MD Anderson Cancer Center
Susan L. Tucker, University of Texas MD Anderson Cancer Center
Wayne D. Newhauser, University of Texas MD Anderson Cancer Center
Radhe Mohan, University of Texas MD Anderson Cancer Center
Lei Dong, University of Texas MD Anderson Cancer Center

Document Type

Article

Publication Date

11-1-2007

Abstract

Purpose: To determine whether a 3-mm isotropic target margin adequately covers the prostate and seminal vesicles (SVs) during administration of an intensity-modulated radiation therapy (IMRT) treatment fraction, assuming that daily image-guided setup is performed just before each fraction. Materials and methods: In-room computed tomographic (CT) scans were acquired immediately before and after a daily treatment fraction in 46 patients with prostate cancer. An eight-field IMRT plan was designed using the pre-fraction CT with a 3-mm margin and subsequently recalculated on the post-fraction CT. For convenience of comparison, dose plans were scaled to full course of treatment (75.6 Gy). Dose coverage was assessed on the post-treatment CT image set. Results: During one treatment fraction (21.4 ± 5.5 min), there were reductions in the volumes of the prostate and SVs receiving the prescribed dose (median reduction 0.1% and 1.0%, respectively, p < 0.001) and in the minimum dose to 0.1 cm3 of their volumes (median reduction 0.5 and 1.5 Gy, p < 0.001). Of the 46 patients, three patients' prostates and eight patients' SVs did not maintain dose coverage above 70 Gy. Rectal filling correlated with decreased percentage-volume of SV receiving 75.6, 70, and 60 Gy (p < 0.02). Conclusions: The 3-mm intrafractional margin was adequate for prostate dose coverage. However, a significant subset of patients lost SV dose coverage. The rectal volume change significantly affected SV dose coverage. For advanced-stage prostate cancers, we recommend to use larger margins or improve organ immobilization (such as with a rectal balloon) to ensure SV coverage. © 2007 Elsevier Ireland Ltd. All rights reserved.

Publication Source (Journal or Book title)

Radiotherapy and Oncology

First Page

251

Last Page

259

Recommended Citation

Melancon, A., O'Daniel, J., Zhang, L., Kudchadker, R., Kuban, D., Lee, A., Cheung, R., de Crevoisier, R., Tucker, S., Newhauser, W., Mohan, R., & Dong, L. (2007). Is a 3-mm intrafractional margin sufficient for daily image-guided intensity-modulated radiation therapy of prostate cancer?. Radiotherapy and Oncology, 85 (2), 251-259. https://doi.org/10.1016/j.radonc.2007.08.008