Magnetic Resonance Imaging-Based BrachytherapyPermanent prostate brachytherapy pubic arch evaluation with diagnostic magnetic resonance imaging
Introduction
Permanent prostate brachytherapy is one treatment option available to men diagnosed with prostate cancer which is able to provide excellent therapeutic outcomes with relatively minimal morbidity [1], [2], [3]. Unfortunately some men are precluded from this treatment modality secondary to anatomic or patient specific factors such as prostate size or the presence of pubic arch interference (PAI) [4], [5]. The assessment for PAI has been traditionally performed before brachytherapy implantation using CT and/or transrectal ultrasound (TRUS) [6], [7]. For CT, a common method of PAI determination consists of outlining the prostate on the largest axial slice and superimposing this over the pelvic bones (6). Overlap of the prostate with the pubic rami of ≤1 cm has been proposed as a threshold value suitable for brachytherapy consideration (8). These methods are generally able to provide an approximate assessment of PAI before brachytherapy implantation but can be subject to operator variability and often require additional testing/procedures in addition to the routine staging and workup for prostate cancer in the modern era.
In recent years, MRI of the pelvis has often replaced CT as the modality of choice for imaging of the prostate and seminal vesicles because of its improved soft tissue delineation and improvements in MRI capabilities over the past decade. MRI is able to provide good sensitivity and specificity for detection of extracapsular extension or seminal vesicle involvement especially with using multiparametric MRI [9], [10], which can lead to altered treatment recommendations especially with regard to brachytherapy candidacy. The use of MRI in the pre-prostatectomy setting has been an area of active on-going research and implementation (11), but its routine clinical adoption in permanent prostate brachytherapy outside staging purposes remains limited (12). The purpose of this study was, therefore, to investigate whether diagnostic MRI performed for the staging of prostate cancer is able to predict PAI in patients being considered for permanent prostate brachytherapy and compare these MRI results to traditional CT- and TRUS-based methods.
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Methods and materials
Forty-one consecutive patients’ charts being considered for brachytherapy at our institution received staging MRI, pre-brachytherapy CT, and TRUS-based simulation. Clinical information, such as demographics, prostate cancer stage, prostate gland size on TRUS, and imaging data, were collected. All patients underwent pelvic MRI with a T2-weighted sequence with endorectal coil (inflated to 30–60 cubic centimeters) as part of their cancer staging. Patients are considered eligible at our institution
Results
The average age for patients at the time of brachytherapy evaluation was 66 years old. All patients but one were classified as having intermediate-risk prostate cancer. The patient with high-risk prostate cancer was evaluated for brachytherapy implant in addition to external beam radiation. The average prostate size (±standard error) on pre-brachytherapy ultrasound was 32.6 ± 2.33 mL. Full details of patient characteristics are summarized in Table 1.
Nineteen patients (46%) exhibited evidence of
Discussion
This study is the first to our knowledge to evaluate PAI before permanent prostate brachytherapy implantation using MRI. Our results show that both MRI and CT provide similar estimates of PAI as determined by TRUS-based brachytherapy simulation, and there was a strong linear correlation between quantitative values of MRI- and CT-based PAI. Furthermore, the ability of MRI to reliably predict lack of PAI was excellent if prostate contour showed no evidence of pubic arch overlap but was less
References (20)
- et al.
Urinary side effects and complications after permanent prostate brachytherapy: the MD Anderson Cancer Center experience
Urology
(2009) - et al.
American Brachytherapy Society consensus guidelines for transrectal ultrasound-guided permanent prostate brachytherapy
Brachytherapy
(2012) - et al.
Use of pelvic CT scanning to evaluate pubic arch interference of transperineal prostate brachytherapy
Int J Radiat Oncol Biol Phys
(1999) - et al.
Use of TRUS to predict pubic arch interference of prostate brachytherapy
Int J Radiat Oncol Biol Phys
(1999) - et al.
Intra-operative pubic arch interference during prostate seed brachytherapy in patients with CT-based pubic arch interference of < or =1cm
Radiother Oncol
(2009) - et al.
Magnetic resonance image guided brachytherapy
Semin Radiat Oncol
(2014) - et al.
Identification of pubic arch interference in prostate brachytherapy: simplifying the transrectal ultrasound technique
Brachytherapy
(2003) - et al.
Magnetic resonance imaging-based treatment planning for prostate brachytherapy
Brachytherapy
(2013) - et al.
Development of multiorgan finite element-based prostate deformation model enabling registration of endorectal coil magnetic resonance imaging for radiotherapy planning
Int J Radiat Oncol Biol Phys
(2007) - et al.
Implanted brachytherapy seed movement reflecting transrectal ultrasound probe-induced prostate deformation
Brachytherapy
(2015)
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Low dose rate brachytherapy for primary treatment of localized prostate cancer: A systemic review and executive summary of an evidence-based consensus statement
2021, BrachytherapyCitation Excerpt :Special consideration should be made for patients with large prostate glands, large median lobes, or prior history of transurethral resection of the prostate (TURP). Patients with large prostate volumes (>60 cc) may benefit from a TRUS (71,72), CT (73), or MRI-guided (74) volume study to ensure minimal pubic arch interference. Such patients may also be at greater risk of urinary retention (75) and late urinary toxicity (76).
Comparison of prostate distortion by inflatable and rigid endorectal MRI coils in permanent prostate brachytherapy imaging
2018, BrachytherapyCitation Excerpt :We believe that MRI provides multiple advantages over ultrasound or CT due to its improved soft tissue delineation, ability to reduce fusion uncertainties, and decrease in the total number of scans/procedures that need to be performed for brachytherapy implantation. For example, in the preimplant setting, MRI has been shown to decrease the number of prostate ultrasound procedures for planning and can replace axial CT imaging for pubic arch interference assessment (31, 32). In the postimplant setting, MRI-only–based dosimetry may also decrease the dose uncertainty arising from CT-MRI fusion (33), and the improved anatomic detail allows for better identification of organs at risk such as the bladder neck or external urinary sphincter, both of which have been associated with prostate brachytherapy dose-related toxicity (34, 35).
Freehand Transperineal Prostate Biopsy with Three-Dimensional Ultrasound Organ-Based Tracking
2021, Journal of Endourology
Funding/Disclaimer: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors declare no conflicts of interest.