The purpose of this study was to establish reproducible guidelines for delineating the clinical target volume (CTV) of the pelvic lymph nodes (LN) by combining the freehand Royal Marsden Hospital (RMH) and Radiation Therapy Oncology Group (RTOG) vascular expansion techniques.
Seven patients with prostate cancer underwent standard planning computed tomography scanning. Four different CTVs (RMH, RTOG, modified RTOG, and Prostate and pelvIs Versus prOsTate Alone treatment for Locally advanced prostate cancer [PIVOTAL] trial) were created for each patient, and 6 different bowel expansion margins (BEM) were created to assess bowel avoidance by the CTV. The resulting CTVs were compared visually and by using Jaccard conformity indices. The volume of overlap between bowel and planning target volume (PTV) was measured to aid selection of an appropriate BEM to enable maximal LN yet minimal normal tissue coverage.
In total, 84 nodal contours were evaluated. LN coverage was similar in all groups, with all of the vascular-expansion techniques (RTOG, modified RTOG, and PIVOTAL), resulting in larger CTVs than that of the RMH technique (mean volumes: 287. 3 cm(3), 326. 7 cm(3), 310. 3 cm(3), and 256. 7 cm(3), respectively). Mean volumes of bowel within the modified RTOG PTV were 19. 5 cm(3) (with 0 mm BEM), 17. 4 cm(3) (1-mm BEM), 10. 8 cm(3) (2-mm BEM), 6. 9 cm(3) (3-mm BEM), 5. 0 cm(3) (4-mm BEM), and 1. 4 cm(3) (5-mm BEM) in comparison with an overlap of 9. 2 cm(3) seen using the RMH technique. Evaluation of conformity between LN-CTVs from each technique revealed similar volumes and coverage.
Vascular expansion techniques result in larger LN-CTVs than the freehand RMH technique. Because the RMH technique is supported by phase 1 and 2 trial safety data, we proposed modifications to the RTOG technique, including the addition of a 3-mm BEM, which resulted in LN-CTV coverage similar to that of the RMH technique, with reduction in bowel and planning target volume overlap. On the basis of these findings, recommended guidelines including a detailed pelvic LN contouring atlas have been produced and implemented in the PIVOTAL trial.
International journal of radiation oncology, biology, physics. 2015 Mar 30 [Epub]
Victoria A Harris, John Staffurth, Olivia Naismith, Alikhan Esmail, Sarah Gulliford, Vincent Khoo, Rebecca Lewis, John Littler, Helen McNair, Azmat Sadoyze, Christopher Scrase, Aslam Sohaib, Isabel Syndikus, Anjali Zarkar, Emma Hall, David Dearnaley, PIVOTAL Trialists
Academic Urology Unit, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, United Kingdom. , Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, Wales, United Kingdom. , Joint Department of Physics, Institute of Cancer Research, and Royal Marsden NHS Foundation Trust, London, United Kingdom. , Ipswich Hospital NHS Foundation Trust, Ipswich, United Kingdom. , Joint Department of Physics, Institute of Cancer Research, and Royal Marsden NHS Foundation Trust, London, United Kingdom. , Academic Urology Unit, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, United Kingdom. , Clinical Trials and Statistics Unit, Institute of Cancer Research, London, United Kingdom. , Clatterbridge Cancer Centre, Liverpool, United Kingdom. , Department of Radiotherapy, The Royal Marsden NHS Foundation Trust, London, United Kingdom. , Beatson West of Scotland Cancer Centre, Scotland, Glasgow, United Kingdom. , Ipswich Hospital NHS Foundation Trust, Ipswich, United Kingdom. , Department of Radiology, The Royal Marsden NHS Foundation Trust, London, United Kingdom. , Clatterbridge Cancer Centre, Liverpool, United Kingdom. , University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom. , Clinical Trials and Statistics Unit, Institute of Cancer Research, London, United Kingdom. , Academic Urology Unit, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, United Kingdom.