title: Mapping of nodal disease in locally advanced prostate cancer: rethinking the clinical target volume for pelvic nodal irradiation based on vascular rather than bony anatomy.
abstract: OBJECTIVE
  Toxicity from pelvic irradiation could be reduced if fields were limited to likely areas of nodal involvement rather than using the standard "four-field box." We employed a novel magnetic resonance lymphangiographic technique to highlight the likely sites of occult nodal metastasis from prostate cancer.
  
  
  METHODS
  Eighteen prostate cancer patients with pathologically confirmed node-positive disease had a total of 69 pathologic nodes identifiable by lymphotropic nanoparticle-enhanced MRI and semiquantitative nodal analysis. Fourteen of these nodes were in the para-aortic region, and 55 were in the pelvis. The position of each of these malignant nodes was mapped to a common template based on its relation to skeletal or vascular anatomy.
  
  
  RESULTS
  Relative to skeletal anatomy, nodes covered a diffuse volume from the mid lumbar spine to the superior pubic ramus and along the sacrum and pelvic side walls. In contrast, the nodal metastases mapped much more tightly relative to the large pelvic vessels. A proposed pelvic clinical target volume to encompass the region at greatest risk of containing occult nodal metastases would include a 2.0-cm radial expansion volume around the distal common iliac and proximal external and internal iliac vessels that would encompass 94.5% of the pelvic nodes at risk as defined by our node-positive prostate cancer patient cohort.
  
  
  CONCLUSIONS
  Nodal metastases from prostate cancer are largely localized along the major pelvic vasculature. Defining nodal radiation treatment portals based on vascular rather than bony anatomy may allow for a significant decrease in normal pelvic tissue irradiation and its associated toxicities.
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA, USA. hshih@partners.org
authors.forename: Helen A
authors.initials: HA
authors.lastname: Shih
authors.forename: Mukesh
authors.initials: M
authors.lastname: Harisinghani
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Zietman
authors.forename: John A
authors.initials: JA
authors.lastname: Wolfgang
authors.forename: Mansi
authors.initials: M
authors.lastname: Saksena
authors.forename: Ralph
authors.initials: R
authors.lastname: Weissleder
mesh_terms: D000368:Aged; D006801:Humans; D015182:Lymphatic Irradiation / Q000379:methods*; D008207:Lymphatic Metastasis / Q000473:pathology* / Q000532:radiotherapy; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000098:blood supply; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods