Open Access

ARTICLE

Stereotactic body radiation therapy with simultaneous integrated boost for prostate cancer: does MRI-targeted biopsy alter the boost field?

Andrew M. Fang¹, Zachary R. Burns¹, Alexander P. Nocera¹, Rex A. Cardan², Jeffrey W. Nix^1,3, Kristin K. Porter^4,*, Andrew M. McDonald^2,3,*, Soroush Rais-Bahrami^1,3,4

1 Department of Urology, University of Alabama at Birmingham, Birmingham, Alabama, USA
2 Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, Alabama, USA
3 O’Neal Comprehensive Cancer Center at UAB, University of Alabama at Birmingham, Birmingham, Alabama, USA
4 Department of Radiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
* these authors contributed equally to this work
Address correspondence to Dr. Soroush Rais-Bahrami, Department of Urology, Faculty Office Tower 1107, 510 20th Street South, Birmingham, AL 35294 USA

Canadian Journal of Urology 2021, 28(5), 10817-10823.

Abstract

Introduction: We aim to investigate if the addition of MRI-US fusion biopsy (FB) can aid in radiation planning and alter the boost field in cases of stereotactic body radiation therapy (SBRT) for prostate cancer with a simultaneous integrated boost (SIB) to a magnetic resonance imaging (MRI)-defined intraprostatic lesion.
Materials and methods: Patients undergoing SBRT with SIB for biopsy-proven prostatic adenocarcinoma and a pre-radiation MRI were retrospectively reviewed. 36.25 Gy in 5 fractions was delivered to the entire prostate along with SIB of 40 Gy to an MRI-defined intraprostatic lesion. Demographic, radiation planning details, and post-procedural outcomes were compared between patients undergoing systematic transrectal ultrasound (TRUS) biopsy followed by MRI to those undergoing an MRI followed by a FB prior to radiation planning.
Results: Forty-three patients underwent systematic TRUS biopsy followed by MRI, and 46 patients underwent FB prior to radiation planning. Patients undergoing systematic TRUS biopsy had a smaller prostate volume when compared to the FB cohort (37.58 ± 13.78 versus 50.28 ± 26.76 cc, p = 0.007). No differences in prostate planning target volume (PTVprostate) and boost volume (PTVboost) were noted, but those undergoing TRUS biopsy prior to MRI had a higher integrated boost volume density (IBVD = PTVboost/total prostate volume) (0.16 ± 0.09 versus 0.13 ± 0.06, p = 0.045). No differences were observed in genitourinary or gastrointestinal toxicity rates.
Conclusions: Compared to systematic TRUS biopsy, implementation of prebiopsy prostate MRI and FB allows for safe and feasible SBRT in patients with significantly larger prostate volumes without increasing SIB cancer-directed treatment volumes, oncologic outcomes, quality of life measures, or treatment-related toxicities.

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