Changes in Target Volumes Definition by Using MRI for Prostate Bed Radiotherapy Planning – Preliminary Results
Authors:
J. Šefrová, Paluska. 1 1; K. Odrážka 2,3,4,5; Z. Bělobrádek 6; P. Hoffmann 6; P. Prošvic 7; M. Broďák 8; M. Louda 8; Z. Mačingová 1; M. Vošmik 1
Authors‘ workplace:
Klinika onkologie a radioterapie, FN Hradec Králové
1; Multiscan s. r. o., Oddělení klinické a radiační onkologie, Pardubická krajská nemocnice, a. s., Pardubice
2; Onkologická klinika 1. LF UK a VFN, Praha
3; Radioterapeutická a onkologická klinika 3. LF UK, Praha
4; Katedra radiační onkologie, IPVZ Praha
5; Radiologická klinika, FN Hradec Králové
6; Urologické oddělení, Oblastní nemocnice Náchod a. s., Náchod
7; Urologická klinika, FN Hradec Králové
8
Published in:
Klin Onkol 2010; 23(4): 256-263
Category:
Original Articles
Overview
Backgrounds:
Magnetic resonance imaging (MRI) is used quite routinely in radiotherapy treatment planning in the primary radiotherapy of prostate cancer as it provides more contrast imaging of soft tissues in the small pelvis than planning CT, thanks to which it allows more exact delineation of target volumes and thus the saving of organs at risk. We tried to verify whether it is possible to use MRI by analogy in the planning of prostate bed radiotherapy.
Patients and Methods:
Twentyone patients indicated for prostate bed radiotherapy were considered in this study. Here we present the preliminary results of 10 of them. Four patients were indicated for adjuvant, 6 for salvage radiotherapy. All the patients underwent, besides standard planning CT, MRI in the same position. Target volumes and organs at risk were delineated into CT, T1 and T2 MRI images – clinical target volume (CTV), planning target volume (PTV), urinary bladder and rectum. Based on the merging of images, the volumes delineated in MRI were copied into planning CT, where the evaluation was done. We evaluated the volumes of each structure, agreement in contouring with the help of the rate of union and intersection of the volumes and with Cohen’s kappa, and 3D differences between volumes of CTV on CT, T1 and T2 MRI.
Results:
Statistically, volumes of CTV and PTV are not significantly different. The volume of the rectum is significantly smaller on T1 and also T2 MRI images. The index of agreement (union/ intersection) is statistically significantly different from 1 for CTV and PTV as well. Cohen’s kappa indicates moderate agreement for CTV CT and T1, T1 and T2 MRI, fair agreement for CTV CT and T2 MRI, and substantial agreement for PTV. In the superior and superolateral direction, the CTV volume on MRI in the central plane is smaller on T1 and T2 images. In the area of seminal vesicles (SV) the cranial border is similar on CT and MRI. In the superoposterior direction, the volume of CTV is smaller on CT than on T1 and T2 MRI, which means, that seminal vesicles are delineated larger in the posterior direction on MRI (about 0.24 cm on T1; by about 0.20 cm on T2 images). In the posterior direction, there are no differences in CTV on CT and T1 while on T2 the CTV is larger (a difference of 0.29 cm). In the posterolateral direction, CTV is smaller on T1 MRI than on CT on both sides, on the right as well as on the left.
Conclusion:
Preliminary results suggest that clinical target volume defined with the help of MRI is shifted compared with CTV defined on planning CT. The agreement of CTV delineation by one radiation oncologist is moderate to fair and is similar to interobserver variability in the contouring of the prostate bed in the planning CT. MRI provides more contrast imaging of the anterior rectal wall, where we have confirmed the most differences in contouring. Moreover, it provides better imaging of local recurrences and seminal vesicles, where the most differences in our group of patients were seen in comparison with planning CT.
Key words:
prostate cancer – radiotherapy – radiotherapy planning – magnetic resonance imaging – clinical target volume
Sources
1. Khoo VS, Padhani AR, Tanner SF et al. Comparison of MRI with CT for the radiotherapy planning of prostate cancer: a feasibility study. Br J Radiol 1999; 72(858): 590– 597.
2. Roach M 3rd, Faillace- Akazawa P, Malfatti C et al. Prostate volumes defined by magnetic resonance imaging and computerized tomographic scans for three- dimensional conformal radiotherapy. Int J Radiat Oncol Biol Phys 1996; 35(5): 1011– 1018.
3. Villeirs GM, L Verstraete K, De Neve WJ et al. Magnetic resonance imaging anatomy of the prostate and periprostatic area: a guide for radiotherapists. Radiother Oncol 2005; 76(1): 99– 106.
4. Rasch C, Barillot I, Remeijer P et al. Definition of the prostate in CT and MRI: a multi‑observer study. Int J Radiat Oncol Biol Phys 1999; 43(1): 57– 66.
5. Debois M, Oyen R, Maes F et al. The contribution of magnetic resonance imaging to the three- dimensional treatment planning of localized prostate cancer. Int J Radiat Oncol Biol Phys 1999; 45(4): 857– 865.
6. Smith WL, Lewis C, Bauman G et al. Prostate volume contouring: a 3D analysis of segmentation using 3DTRUS, CT, and MR. Int J Radiat Oncol Biol Phys 2007; 67(4): 1238– 1247.
7. Wiltshire KL, Brock KK, Haider MA et al. Anatomic boundaries of the clinical target volume (prostate bed) after radical prostatectomy. Int J Radiat Oncol Biol Phys 2007; 69(4): 1090– 1099.
8. Allen SD, Thompson A, Sohaib SA. The normal post‑surgical anatomy of the male pelvis following radical prostatectomy as assessed by magnetic resonance imaging. Eur Radiol 2008; 18(6): 1281– 1291.
9. Poortmans P, Bossi A, Vandeputte K et al. EORTC Radiation Oncology Group. Guidelines for target volume definition in post‑operative radiotherapy for prostate cancer, on behalf of the EORTC Radiation Oncology Group. Radiother Oncol 2007; 84(2): 121– 127.
10. Cohen J. A coefficient of agreement for nominal scales. Educational and Psychological Measurement 1960; 20(1): 37– 46.
11. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977; 33(1): 159– 174.
12. Sella T, Schwartz LH, Swindle PW et al. Suspected local recurrence after radical prostatectomy: endorectal coil MR imaging. Radiology 2004; 231(2): 379– 385.
13. Silverman JM, Krebs TL. MR imaging evaluation with a transrectal surface coil of local recurrence of prostatic cancer in men who have undergone radical prostatectomy. AJR Am J Roentgenol 1997; 168(2): 379– 385.
14. Meijer GJ, de Klerk J, Bzdusek K et al. What CTV- to- PTV margins should be applied for prostate irradiation? Four- dimensional quantitative assessment using model‑based deformable image registration techniques. Int J Radiat Oncol Biol Phys 2008; 72(5): 1416– 1425.
15. Wong JR, Gao Z, Uematsu M et al. Interfractional prostate shifts: review of 1870 computed tomography (CT) scans obtained during image- guided radiotherapy using CT- on- rails for the treatment of prostate cancer. Int J Radiat Oncol Biol Phys 2008; 72(5): 1396– 1401.
16. Nyholm T, Nyberg M, Karlsson MG et al. Systematisation of spatial uncertainties for comparison between a MR and a CT‑based radiotherapy workflow for prostate treatments. Radiat Oncol 2009; 4: 54.
17. McLaughlin PW, Narayana V, Drake DG et al. Comparison of MRI pulse sequences in defining prostate volume after permanent implantation. Int J Radiat Oncol Biol Phys 2002; 54(3): 703– 711.
18. Sella T, Schwartz LH, Hricak H. Retained seminal vesicles after radical prostatectomy: frequency, MRI characteristics, and clinical relevance. AJR Am J Roentgenol 2006; 186(2): 539– 546.
19. Michalski JM, Lawton C, El Naqa I et al. Development of RTOG consensus guidelines for the definition of the clinical target volume for postoperative conformal radiation therapy for prostate cancer. Int J Radiat Oncol Biol Phys 2010; 76(2): 361– 368.
Labels
Paediatric clinical oncology Surgery Clinical oncologyArticle was published in
Clinical Oncology
2010 Issue 4
Most read in this issue
- Merkel Cell Skin Carcinoma
- Metastatic Breast Cancer in 28 Years Old Man
- Bile Duct Malignancies
- Targeted Therapy with an EGFR Tyrosine Kinase Inhibitor in Bronchioloalveolar Carcinoma of the Lung: A Literature Review and a Case Study of Clinically Prompt and Intensive Response to Erlotinib.