ABSTRACT
PURPOSE
Implant quality metrics as measured by D90 and V100 do not address the adequacy of
periprostatic margins. Relative margin deficiencies may relate to efficacy and margin
excesses to post-implant toxicity. Our purpose is to determine MRI-defined treatment
margins on prostate achieved with LDR brachytherapy.
METHODS AND MATERIALS
Post implant CT and MR images from 487 consecutive patients who received LDR brachytherapy
from 2010 to 14 were co-registered. Four prostate quadrants were defined; anterior-superior
(AS), posterior-superior (PS), anterior-inferior (AI), posterior-inferior (PI). Dosimetric
variables were measured for prostate, and for each quadrant with a 0-, 2-, 3-, and
5-mm margin, as well as for the membranous urethra defined on MRI.
RESULTS
Prostate D90 (no margin) was associated with D90 to the volume enclosed by 2 mm, 3
mm and 5 mm margins (R2 = 0.9 – 1.0) with an average 7.1% decrease in dose per mm
of margin. Mean D90 for PS, AI and PI quadrants were > 110% of prescription dose for
margins of 2-, 3-, and 5-mm. AS quadrant mean D90s were generally lower (83.2% for
2 mm, 76.4% for 3 mm and 62.2% for 5 mm). Urethral strictures (n = 9) were associated with higher doses in the AI quadrant, and higher membranous
urethral V125 (51 vs. 32%, p 0.013) and V150 (34.5 vs. 17.6%, p 0.01).
CONCLUSIONS
Using MR-CT post implant dosimetry, margin coverage up to 5 mm was excellent with
less margin coverage in the AS quadrant. Late ≥ grade 2 toxicity and urinary strictures
are more likely to occur with relative margin excess in the anterior-inferior quadrant
and higher doses caudal to the prostate apex. Within this analysis, there was no relationship
between treatment margins, and PSA outcome.
Keywords
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References
- Population-based 10-year oncologic outcomes after low-dose-rate brachytherapy for low-risk and intermediate risk prostate cancer.Cancer. 2013; 119: 1537-1546
- 10-year experience with I-125 prostate brachytherapy at the Princess Margaret Hospital: results for 1 100 patients.Int. J. Radiation Oncology Biol. Phys. 2011; 80: 1323-1329
Morris J.W., Tyldesley S., Pai H., et al. ASCENDE-RT: a multi-center, randomized trial of dose-escalated external beam radiation therapy (EBRT-B) versus low-dose-rate brachtherapy (LDR-B) for men with unfavourable-risk localized prostate cancer.
- Whole prostate D90 and V100: a dose-response analysis of 2000 consecutive 125I monotherapy patients.Brachytherapy. 2014; : 32-41
- Customized dose prescription for permanent prostate brachytherapy: insights from a multicentre analysis of dosimetry outcomes.Int. J. Radiation oncology Biol. Phys. 2007; 69: 1472-1477
- Predictors of extracapsular extension and its radial distance in prostate cancer: implications for prostate IMRT, brachytherapy, and surgery.Cancer Journal. 2003; 9: 454-460
- Clinicopathologic analysis of extracapsular extension in prostate cancer: should the clinical target volume be expanded posteriolaterally to account for microscopic extension?.Int J Radiation Oncology Biol Phys. 2006; 65: 999-1007
- Extent of extracapsular extension in localized prostate cancer.Urology. 2000; 55: 382-386
- Cancer. 1999; 85: 2630-2637
- Magnetic resonance imaging-defined treatment margins in iodine-125 prostate brachytherapy.Int J Radiation Oncology Biol Phys. 2010; 77: 1079-1084
- ASCENDE-RT: An analysis of treatment-related morbidity for a randomized trial comparing a low-dose-rate brachytherapy boost with a dose-escalated external beam boost for high- and intermediate-risk prostate cancer.Int J Radiation Oncology Biol Phys. 2017; 98: 286-295
- Evaluation of dosimetric parameters and disease response after 125 iodine transperineal brachytherapy for low- and intermediate-risk prostate cancer.Int J Radiat Oncol Biol Phys. 2009; 73: 1432-1438
- Defining a magnetic resonance scan sequence for permanent seed prostate brachytherapy postimplant assessment.Brachytherapy. 2013; 12: 25-29
- The dosimetry of prostate brachytherapy-induced urethral strictures.Int J Radiat Oncol Biol Phys. 2002; 52: 461-468
- Risk factors for the development of prostate brachytherapy related urethral strictures.J Urol. 2006; 175: 1376-1380
- Regional treatment margins for prostate brachytherapy.Brachytherapy. 2013; 12: 596-602
- Multisector prostate dosimetric quality: analysis of a large community database.Brachytherapy. 2014; 13: 146-151
- Regional dose metrics as predictors of biochemical recurrence after low-dose-rate prostate brachytherapy.Brachytherapy. 2015; 14: 350-358
- Dose to the bladder neck is the most important predictor for acute and late toxicity after low-dose-rate prostate brachytherapy: implications for establishing new dose constraints for treatment planning.Int J Radiat Oncol Biol Phys. 2014; 90: 312-319
- Treatment margins predict biochemical outcomes after prostate brachytherapy.Cancer J. 2004; 10: 175-180
- The measurement of membranous urethral length using transperineal ultrasound prior to radical prostatectomy.Scand J Urol. 2018; 52: 263-268
- A biochemical definition of cure after brachytherapy for prostate cancer.Radiother Oncol. 2020; 149: 64-69
Article info
Publication history
Accepted:
November 24,
2021
Received in revised form:
November 3,
2021
Received:
June 23,
2021
Identification
Copyright
© 2021 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.
