title: Incidental Dose to Pelvic Nodal Regions in Prostate-Only Radiotherapy.
abstract: Pelvic lymph nodal regions receive an incidental dose from conformal treatment of the prostate. This study was conducted to investigate the doses received by the different pelvic nodal regions with varying techniques used for prostate radiotherapy.
  
  
  
  Twenty patients of high-risk node-negative prostate cancer treated with intensity-modulated radiotherapy to the prostate alone were studied. Replanning was done for intensity-modulated radiotherapy, 3-dimensional conformal treatment, and 2-dimensional conventional radiotherapy with additional delineation of the pelvic nodal regions, namely, common iliac (upper and lower), presacral, internal iliac, obturator, and external iliac. Dose-volume parameters such as Dmean, D100%, D66%, D33%, V40, and V50 to each of the nodal regions were estimated for all patients.
  
  
  
  The obturator nodes received the highest dose among all nodal regions. The mean dose received by obturator nodal region was 44, 29, and 22 Gy from 2-dimensional conventional radiotherapy, 3-dimensional conformal treatment, and intensity-modulated radiotherapy, respectively. The mean dose was significantly higher when compared between 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment ( P < .001), 2-dimensional conventional radiotherapy and intensity-modulated radiotherapy ( P < .001), and 3-dimensional conformal treatment and intensity-modulated radiotherapy ( P < .001). The D33% of the obturator region was 64, 39, and 37 Gy from 2-dimensional conventional radiotherapy, 3-dimensional conformal treatment, and intensity-modulated radiotherapy, respectively. The dose received by all other pelvic nodal regions was low and not clinically relevant.
  
  
  
  The incidental dose received by obturator regions is significant especially with 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment techniques as used in the trials studying elective pelvic nodal irradiation. However, with intensity-modulated radiotherapy, this dose is lower, making elective pelvic irradiation more relevant. Advances in Knowledge: This study highlights that incidental dose received by obturator regions is significant especially with 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment techniques.
authors: 1 Department of Radiation Oncology, Tata Memorial Centre, Mumbai, India.
authors: Vedang
authors: V
authors: Murthy
authors: 1 Department of Radiation Oncology, Tata Memorial Centre, Mumbai, India.
authors: Shirley
authors: S
authors: Lewis
authors: 2 Department of Medical Physics, Tata Memorial Centre, Mumbai, India.
authors: Mayur
authors: M
authors: Sawant
authors: 2 Department of Medical Physics, Tata Memorial Centre, Mumbai, India.
authors: Siji N
authors: SN
authors: Paul
authors: 1 Department of Radiation Oncology, Tata Memorial Centre, Mumbai, India.
authors: Umesh
authors: U
authors: Mahantshetty
authors: 1 Department of Radiation Oncology, Tata Memorial Centre, Mumbai, India.
authors: Shyam Kishore
authors: SK
authors: Shrivastava
mesh_terms: D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects*; D008297:Male; D058958:Organs at Risk; D010388:Pelvis / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D014057:Tomography, X-Ray Computed
keywords: incidental dose; pelvic nodes; prostate cancer