Prostate-Centric Versus Bony-Centric Registration in the Definitive Treatment of Node-Positive Prostate Cancer with Simultaneous Integrated Boost: A Dosimetric Comparison

Trudy C. Wu, MD; Michael Xiang, MD, PhD; Nicholas G. Nickols, MD, PhD; Stephen Tenn, PhD; Nzhde Agazaryan, PhD; John V. Hegde, MD; Michael L. Steinberg, MD; Minsong Cao, PhD; Amar U. Kishan, MD

Advances in Radiation Oncology (Jul 2022)

Prostate-Centric Versus Bony-Centric Registration in the Definitive Treatment of Node-Positive Prostate Cancer with Simultaneous Integrated Boost: A Dosimetric Comparison

Trudy C. Wu, MD,
Michael Xiang, MD, PhD,
Nicholas G. Nickols, MD, PhD,
Stephen Tenn, PhD,
Nzhde Agazaryan, PhD,
John V. Hegde, MD,
Michael L. Steinberg, MD,
Minsong Cao, PhD,
Amar U. Kishan, MD

Affiliations

Trudy C. Wu, MD: Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California
Michael Xiang, MD, PhD: Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California
Nicholas G. Nickols, MD, PhD: Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California; Department of Radiation Oncology, VA Greater Los Angeles Healthcare System, Los Angeles, California
Stephen Tenn, PhD: Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California
Nzhde Agazaryan, PhD: Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California
John V. Hegde, MD: Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California
Michael L. Steinberg, MD: Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California
Minsong Cao, PhD: Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California
Amar U. Kishan, MD: Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California; Department of Urology, University of California, Los Angeles, Los Angeles, California; Corresponding author: Amar U. Kishan.

Journal volume & issue: Vol. 7, no. 4
p. 100944

Abstract

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Purpose: To determine the effect of daily shifts based on rigid registration to intraprostatic markers on coverage of boost doses delivered to gross nodal disease for prostate cancer. Methods and Materials: Seventy-five cone beam computed tomographies (CBCTs) from 15 patients treated with definitive radiation for clinically node-positive prostate cancer underwent fiducial-based and pelvic bony-based registration to the initial planning scans. Gross tumor volumes of nodal boost targets were contoured directly on each CBCT registration. The nodal displacement (3-dimensional translation from the node centroid on planning CT to node centroid on registered CBCT) and dose coverage (minimum dose [Dmin], mean dose [Dmean], dose delivered to 95% of the gross tumor volumes [D95]) were calculated for each registration on all nodal targets. All doses for each node were normalized to its intended prescription dose (dose covering 95% of a 3 mm planning target volume [PTV] expansion). Results: Forty-one gross nodal targets were analyzed. Most boosted nodes (80.5%, 33/41) were treated with conventional fractionation using volumetric-arc radiation therapy, and 19.5% (8/41) underwent stereotactic body radiation therapy (SBRT). Dmin, Dmean, and D95 were all significantly lower with fiducial-based registration compared with bony-based registration (P < .0001). Nodal displacement was significantly higher for fiducial-based registrations (P < .0001). The 3-dimensional translation between the fiducial-based and bony-based registrations (bony-to-fiducial vector) was the most significant predictor of nodal displacement (P < .0001). On fiducial-based registrations, a 3 to 5 mm gross nodal PTV margin is sufficient in most directions; however, superior and posterior margins of 8 to 9 mm are required as a result of asymmetrical prostatic motion. Conclusions: Large and anisotropic PTV margins are likely needed to adequately dose gross nodal targets when patient setup is based on rigid registration to intraprostatic markers. Alternative approaches such as adaptive replanning may be required to overcome these limitations.

Published in Advances in Radiation Oncology

ISSN: 2452-1094 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Medicine: Medicine (General): Medical physics. Medical radiology. Nuclear medicine; Medicine: Internal medicine: Neoplasms. Tumors. Oncology. Including cancer and carcinogens
Website: http://www.journals.elsevier.com/advances-in-radiation-oncology/

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