title: Pancreatic cancer tumor size on CT scan versus pathologic specimen: implications for radiation treatment planning.
abstract: OBJECTIVE
  Pancreatic cancer primary tumor size measurements are often discordant between computed tomography (CT) and pathologic specimen after resection. Dimensions of the primary tumor are increasingly relevant in an era of highly conformal radiotherapy.
  
  
  METHODS
  We retrospectively evaluated 97 consecutive patients with resected pancreatic cancer at two Boston hospitals. All patients had CT scans before surgical resection. Primary endpoints were maximum dimension (in millimeters) of the primary tumor in any direction as reported by the radiologist on CT and by the pathologist for the resected gross fresh specimen. Endoscopic ultrasound (EUS) findings were analyzed if available.
  
  
  RESULTS
  Of the patients, 87 (90%) had preoperative CT scans available for review and 46 (47%) had EUS. Among proximal tumors (n = 69), 40 (58%) had pathologic duodenal invasion, which was seen on CT in only 3 cases. The pathologic tumor size was a median of 7 mm larger compared with CT size for the same patient (range, -15 to 43 mm; p < 0.0001), with 73 patients (84%) having a primary tumor larger on pathology than CT. Endoscopic ultrasound was somewhat more accurate, with pathologic tumor size being a median of only 5 mm larger compared with EUS size (range, -15 to 35 mm; p = 0.0003).
  
  
  CONCLUSIONS
  Computed tomography scans significantly under-represent pancreatic cancer tumor size compared with pathologic specimens in resectable cases. We propose a clinical target volume expansion formula for the primary tumor based on our data. The high rate of pathologic duodenal invasion suggests a risk of duodenal under-coverage with highly conformal radiotherapy.
authors: Harvard Radiation Oncology Program, Boston, MA, USA.
authors: Nils D
authors: ND
authors: Arvold
authors: Andrzej
authors: A
authors: Niemierko
authors: Harvey J
authors: HJ
authors: Mamon
authors: Carlos
authors: C
authors: Fernandez-del Castillo
authors: Theodore S
authors: TS
authors: Hong
mesh_terms: D004379:Duodenal Neoplasms / Q000473:pathology; D006801:Humans; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000379:methods; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden; D014463:Ultrasonography