title: Clinical target volume in postoperative radiotherapy for gastric cancer: identification of major difficulties and controversies.
abstract: OBJECTIVE
  To identify the main difficulties in postoperative clinical target volume (CTV) delineation in gastric cancer (GC).
  
  
  METHODS
  Before and after a training course, 20 radiation oncology residents were asked to delineate the CTV for the postoperative GC case on four computed tomography scans: dome of the diaphragm, anterior abdominal wall, duodenal stump and porta hepatis level, and to determine the lower CTV border. CTV volume was reconstructed from requested planar contours. Area of intersection (AI) for each requested scan and volume of intersection (VI), defined as the overlap of delineated area/volume with respective reference area (RA)/reference volume (RV) proposed by the senior radiation oncologist, were computed. The degree of agreement between the reference and participants' contours was quantified using the Concordance Index (CI): AI/RA × 100% or VI/RV × 100%. The lower CTV border was analyzed separately. Pre- and post-training CIs were compared. A questionnaire investigated the difficulties with contouring.
  
  
  RESULTS
  Mean CI value was the lowest for the dome of the diaphragm (24% pre-training, 35 % post-training) and for the duodenal stump (49% pre-training, 61% post-training). Mean CI for the CTV volume was 49% pre-training and 59% post-training, p = 0.39. Mean distance from the reference to the participants' lower CTV borders was 2.73 cm pre-training and 2.0 cm post-training, p = 0.71. In a questionnaire, 75% of respondents indicated the elective nodal area as the main difficulty.
  
  
  CONCLUSIONS
  Delineation of the dome of the diaphragm and the duodenal stump, as yet not recognized as the source of variation, should be addressed in the international consensus guidelines and clarified.
authors: Radiotherapy Department, Regional Oncology Center, ul. Bialska 104/118, 42-200, Czestochowa, Poland. sochajoanna@wp.pl.
authors: J
authors: J
authors: Socha
authors: Radiotherapy Department, Independent Public Health Care Facility of the Ministry of the Interior and Warmian & Mazurian Oncology Centre, Olsztyn, Poland.
authors: G
authors: G
authors: Wołąkiewicz
authors: Radiotherapy Department, Independent Public Health Care Facility of the Ministry of the Interior and Warmian & Mazurian Oncology Centre, Olsztyn, Poland.
authors: E
authors: E
authors: Wasilewska-Teśluk
authors: Radiotherapy Department, Greater Poland Cancer Center, Poznan, Poland.
authors: P
authors: P
authors: Janiga
authors: Radiotherapy Department, Subcarpathian Cancer Center, Brzozow, Poland.
authors: T
authors: T
authors: Kondraciuk
authors: Radiotherapy Department, West Pomeranian Oncology Center, Szczecin, Poland.
authors: A
authors: A
authors: Majewska
authors: Radiotherapy Department, Regional Oncology Center, Tarnów, Poland.
authors: K
authors: K
authors: Olearski
authors: Radiotherapy Department, Independent Public Health Care Facility of the Ministry of the Interior and Warmian & Mazurian Oncology Centre, Olsztyn, Poland.
authors: L
authors: L
authors: Kępka
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D005743:Gastrectomy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D015588:Observer Variation; D011182:Postoperative Care; D017410:Practice Guidelines as Topic / Q000592:standards*; D011379:Prognosis; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D013274:Stomach Neoplasms / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D047368:Tumor Burden
keywords: Adjuvant radiotherapy; Gastric cancer; Interobserver variation; Radiotherapy planning; Volume delineation