Does a Dominant Intraprostatic Lesion Boost Require Daily Adaptation when Treated with Stereotactic Online Adaptive MR-Guided Therapy?

Document Type

Conference Proceeding

Publication Date

10-1-2023

Publication Title

Int J Radiat Oncol Biol Phys

Keywords

adult, bladder neck, cancer patient, clinical article, conference abstract, human, male, organs at risk, physician, practice guideline, prescription, prospective study, prostate cancer, quality of life, re-irradiation, rectum, stereotactic body radiation therapy, surgery, urethra

Abstract

Purpose/Objective(s): Multiple trials have demonstrated a dose-response relationship for radiation therapy in the treatment of localized prostate cancer. Recent data has also demonstrated a benefit with whole gland stereotactic radiation therapy (SBRT) in conjunction with a simultaneous integrated boost to the dominant intraprostatic lesion (DIL). SBRT with a DIL boost can often increase dose to nearby organs at risk such as the rectum and online adaptive MR guided radiation therapy (MGgRT) may offer a dosimetric and toxicity benefit. Materials/Methods: A prospective database of MRgRT patients was queried for intact prostate cancer patients who received SBRT with a SIB to the DIL. The guideline for adaptation for coverage was to ensure the PTV-prostate coverage at 95% of prescribed dose was greater than 92% or by discretion of the treating physician. Adaptions for organs at risk were made to meet prescription constraints. The number of fractions requiring adaptation to meet organs at risk constraints and/or adequate coverage were reviewed. Results: A total of 26 patients were treated with SBRT with a DIL boost using stereotactic online adaptive MRgRT from 2020 to 2022. 10 of 26 patients were treated for re-irradiation of intact prostate. Out of the 130 fractions delivered, 107 fractions required adaptation (82.3%). 59 fractions were adapted for urethra (45.2%), 48 fractions were adapted for bladder (36.9%), 36 fractions were adapted for rectum (27.7%), 23 fractions were adapted for bladder neck (17.7%), and 19 fractions were adapted for coverage (14.6%). For 53 fractions (40.8 %), adaptation was required for more than one organ at risk. Conclusion: A total of 82.3% of fractions required adaptation for patients treated with SBRT with a DIL boost using stereotactic online adaptive MRgRT. Adaptation occurred most frequently for urethral (45.2%), bladder (36.9%), and rectal constraints (27.7%). Further studies are needed to elucidate if daily adaptive online MRgRT translates to reduced patient toxicity and improved quality of life.

Volume

117

Issue

2

First Page

e374

Last Page

e375

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