Dosimetric evaluation of inclusion of proximal seminal vesicle in target volume in low-risk prostate cancer treated with stereotactic body radiotherapy

Year 2023, Volume: 5 Issue: 3, 253 - 260, 28.07.2023

Ela Delikgöz Soykut , Hatice Tataroğlu

https://doi.org/10.38053/acmj.1320219

Abstract

Aims: Ultra hypofractionation using stereotactic body radiotherapy (SBRT) for low-risk PCa is considered a viable treatment option. The target volume for ultra hypofractionated RT was determined as prostate and/or proximal seminal vesicles; however, there are no clear guidelines on when to add a proximal seminal vesicle to the target volume. We aimed to dosimetrically assess the effect of inclusion of the proximal seminal vesicle in the planning target volume (PTV) on the dose distribution of organ at risk (OAR) when SBRT is administered to patients with low-risk PCa.
Methods: Low-risk PCa cases who underwent SBRT with CyberKnife were retrospectively screened, and 20 random cases were included. The contours of OARs and target volumes were checked as recommended in international contouring atlases by the same radiation oncologist. Two treatment plans by determining two different PTV (prostate alone in plan 1 and prostate with proximal seminal vesicles in plan 2) were made by the same specialist physicist. 5×7.25 Gy was chosen as the dose schedule defined for both plans.
Results: Regarding coverage, homogeneity index, and new conformity index (nCI), there was no significant difference between the two plans (p=0.397, p=0.452, p=0.225). The plan 2 had a greater PTV Dmax (p<0.001). There was better conformity index at plan 1, as well as lower monitor unit and beam on time (p<0.05). The plan 1 had statistically lower values for each treatment parameter assessed for bladder (p<0.05). The treatment parameters evaluated for the rectum were statistically lower in the plan 1, except for V32.625 (p<0.05). The plan 1 was statistically better in terms of V29.5 for the penile bulb and V37.5 and V38 for neurovascular bundles (p<0.05). There was no significant difference between the two plans in terms of femoral heads and bowel (p=0.180, p=0.209, p=0.398, p=0.726, p=0.053, p=0.068). In addition, regardless of plan type, a majority of treatment parameters for bladder were statistically significantly affected in plans with a PTV volume greater than 100 cc (p<0.05).
Conclusion: In low-risk PCa, inclusion of the proximal seminal vesicle in the target volume may be overlooked as quantitatively insignificant increases in high-dose OAR volumes as they do not exceed dose constraints in routine clinical practice, and these high-dose OAR volumes are likely to be important in the development of toxicity. We recommend that special attention be paid to the high doses exposed in OARs in low-risk PCa. In addition, it should be kept in mind that bladder toxicity may increase with increasing PTV volume, especially above 100 cc.

Keywords

Low-risk, prostate cancer, prostate, seminal vesicle, stereotactic body radiotherapy, target volume

References

• Madalinska JB, Essink-Bot ML, de Koning HJ, Kirkels WJ, van der Maas PJ, Schröder FH. Health-related quality-of-life effects of radical prostatectomy and primary radiotherapy for screen-detected or clinically diagnosed localized prostate cancer. J Clin Oncol. 2001;19(6):1619-1628. doi:10.1200/JCO.2001.19.6.1619
• Miralbell R, Roberts SA, Zubizarreta E, Hendry JH. Dose-fractionation sensitivity of prostate cancer deduced from radiotherapy outcomes of 5,969 patients in seven international institutional datasets: α/β = 1.4 (0.9-2.2) Gy. Int J Radiat Oncol Biol Phys. 2012;82(1):e17-e24. doi:10.1016/j.ijrobp.2010.10.075
• Fowler JF. The radiobiology of prostate cancer including new aspects of fractionated radiotherapy. Acta Oncol. 2005;44(3):265-276. doi:10.1080/02841860410002824
• Dearnaley D, Syndikus I, Mossop H, et al. Conventional versus hypofractionated high-dose intensity-modulated radiotherapy for prostate cancer: 5-year outcomes of the randomised, non-inferiority, phase 3 CHHiP trial. Lancet Oncol. 2016;17(8):1047-1060. doi:10.1016/S1470-2045(16)30102-4
• Incrocci L, Wortel RC, Alemayehu WG, et al. Hypofractionated versus conventionally fractionated radiotherapy for patients with localised prostate cancer (HYPRO): final efficacy results from a randomised, multicentre, open-label, phase 3 trial. Lancet Oncol. 2016;17(8):1061-1069. doi:10.1016/S1470-2045(16)30070-5
• King CR, Freeman D, Kaplan I, et al. Stereotactic body radiotherapy for localized prostate cancer: pooled analysis from a multi-institutional consortium of prospective phase II trials. Radiother Oncol. 2013;109(2):217-221. doi:10.1016/j.radonc.2013.08.030
• Brand DH, Tree AC, Ostler P, et al. Intensity-modulated fractionated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): acute toxicity findings from an international, randomised, open-label, phase 3, non-inferiority trial. Lancet Oncol. 2019;20(11):1531-1543. doi:10.1016/S1470-2045(19)30569-8
• Gay HA, Barthold HJ, O’Meara E, et al. Pelvic normal tissue contouring guidelines for radiation therapy: a Radiation Therapy Oncology Group consensus panel atlas.. Int J Radiat Oncol Biol Phys. 2012;83(3):e353-e362. doi:10.1016/j.ijrobp.2012.01.023
• Salembier C, Villeirs G, De Bari B, et al. ESTRO ACROP consensus guideline on CT- and MRI-based target volume delineation for primary radiation therapy of localized prostate cancer. Radiother Oncol. 2018;127(1):49-61. doi:10.1016/j.radonc.2018.01.014
• Wright JL, Newhouse JH, Laguna JL, Vecchio D, Ennis RD. Localization of neurovascular bundles on pelvic CT and evaluation of radiation dose to structures putatively involved in erectile dysfunction after prostate brachytherapy. Int J Radiat Oncol Biol Phys. 2004;59(2):426-435. doi:10.1016/j.ijrobp.2003.11.022
• Eastham JA, Auffenberg GB, Barocas DA, et al. Clinically Localized Prostate Cancer: AUA/ASTRO Guideline. Part III: Principles of Radiation and Future Directions. J Urol. 2022;208(1):26-33. doi:10.1097/JU.0000000000002759
• Grimm J, LaCouture T, Croce R, Yeo I, Zhu Y, Xue J. Dose tolerance limits and dose volume histogram evaluation for stereotactic body radiotherapy. J Appl Clin Med Phys. 2011;12(2):3368. doi:10.1120/jacmp.v12i2.3368
• Widmark A, Gunnlaugsson A, Beckman L, et al. Ultra-hypofractionated versus conventionally fractionated radiotherapy for prostate cancer: 5-year outcomes of the HYPO-RT-PC randomised, non-inferiority, phase 3 trial. Lancet. 2019;394(10196):385-395. doi:10.1016/S0140-6736(19)31131-6
• Fransson P, Nilsson P, Gunnlaugsson A, et al. Ultra-hypofractionated versus conventionally fractionated radiotherapy for prostate cancer (HYPO-RT-PC): patient-reported quality-of-life outcomes of a randomised, controlled, non-inferiority, phase 3 trial. Lancet Oncol. 2021;22(2):235-245. doi:10.1016/S1470-2045(20)30581-7
• Bolzicco G, Favretto MS, Scremin E, Tambone C, Tasca A, Guglielmi R. Image-guided stereotactic body radiation therapy for clinically localized prostate cancer: preliminary clinical results. Technol Cancer Res Treat. 2010;9(5):473-477. doi:10.1177/153303461000900505
• Katz A. Stereotactic body radiotherapy for low-risk prostate cancer: a ten-year analysis. Cureus. 2017;9(9):e1668. doi:10.7759/cureus.1668
• Musunuru HB, Quon H, Davidson M, et al. Dose-escalation of five-fraction SABR in prostate cancer: Toxicity comparison of two prospective trials. Radiother Oncol. 2016;118(1):112-117. doi:10.1016/j.radonc.2015.12.020
• King CR, Collins S, Fuller D, et al. Health-related quality of life after stereotactic body radiation therapy for localized prostate cancer: results from a multi-institutional consortium of prospective trials. Int J Radiat Oncol Biol Phys. 2013;87(5):939-945. doi:10.1016/j.ijrobp.2013.08.019
• Gomez CL, Xu X, Qi XS, et al. Dosimetric parameters predict short-term quality-of-life outcomes for patients receiving stereotactic body radiation therapy for prostate cancer. Pract Radiat Oncol. 2015;5(4):257-262. doi:10.1016/j.prro.2015.01.006
• Qi XS, Wang JP, Gomez CL, et al. Plan quality and dosimetric association of patient-reported rectal and urinary toxicities for prostate stereotactic body radiotherapy. Radiother Oncol. 2016;121(1):113-117. doi:10.1016/j.radonc.2016.08.012
• Seymour ZA, Chang AJ, Zhang L, et al. Dose-volume analysis and the temporal nature of toxicity with stereotactic body radiation therapy for prostate cancer. Pract Radiat Oncol. 2015;5(5):e465-e472. doi:10.1016/j.prro.2015.02.001
• Iarrobino NA, Gill B, Sutera PA, Kalash R, D’ Ambrosio D, Heron DE. Early Exploratory Analysis for Patient-reported Quality of Life and Dosimetric Correlates in Hypofractionated Stereotactic Body Radiation Therapy (SBRT) for Low-risk and Intermediate-risk Prostate Cancer: Interim Results from a Prospective Phase II Clinical Trial. Am J Clin Oncol. 2019;42(11):856-861. doi:10.1097/COC.0000000000000586
• Wang K, Chen RC, Kane BL, et al. Patient and Dosimetric Predictors of Genitourinary and Bowel Quality of Life After Prostate SBRT: Secondary Analysis of a Multi-institutional Trial. Int J Radiat Oncol Biol Phys. 2018;102(5):1430-1437. doi: 10.1016/j.ijrobp.2018.07.191
• Repka MC, Carrasquilla M, Paydar I, et al. Dosimetric predictors of acute bowel toxicity after Stereotactic Body Radiotherapy (SBRT) in the definitive treatment of localized prostate cancer. Acta Oncol. 2023;62(2):174-179. doi:10.1080/0284186X.2023.2180661
• Wiegner EA, King CR. Sexual function after stereotactic body radiotherapy for prostate cancer: results of a prospective clinical trial. Int J Radiat Oncol Biol Phys. 2010;78(2):442-448. doi:10.1016/j.ijrobp.2009.07.1748
• Obayomi-Davies O, Chen LN, Bhagat A, et al. Potency preservation following stereotactic body radiation therapy for prostate cancer. Radiat Oncol. 2013;8:256. doi:10.1186/1748-717X-8-256