title: Pancreatic cancer adjuvant radiotherapy target volume design: based on the postoperative local recurrence spatial location.
abstract: OBJECTIVE
  To explore the areas at highest risk for postoperative pancreatic cancer local recurrence according to the spatial location of local failures, with the aim to provide a precise target volume for pancreatic cancer adjuvant radiotherapy.
  
  
  METHODS
  Patients with pancreatic cancer who had undergone surgery for the primary tumor in pancreas at our institution from January 2010 to August 2015 were retrospectively analyzed. All local recurrences were plotted on the computed tomography (CT) image of a representative patient according to their relative coordinates to superior mesenteric artery (SMA) or celiac axis (CA). Adjuvant radiation clinical target volume (CTV)-90 and CTV-80 were created to cover 90 % and 80 % plotted recurrences. This planning approach was applied in four simulated cases with comparison to the plan according to RTOG 0848 contouring consensus guidelines. Raystation v4.5.1.14 was used for analyzing high throughput physics data.
  
  
  RESULTS
  Eighty-three patients with local recurrence were included from 305 postoperative pancreatic cancer patients who did not receive adjuvant radiotherapy. Thirty-one (37 %) patients did not have adjuvant therapy at all, 52 (63 %) patients undergone adjuvant chemotherapy alone. Spatial location of local failure was created. Most recurrences occurred near CA or SMA. CTV-90 was generated through expanding the combined SMA and CA contours by 30 mm right-lateral, 21 mm left-lateral, 20 mm anterior, 13 mm posterior, 10 mm superior, and 20 mm inferior. CTV-80, smaller in volume, was also created for simultaneous integrated boost. Through comparison and analysis of the simulated cases, the radiation volumes proposed were much smaller than those with RTOG 0848 contouring consensus guidelines (average volume: PTV-80 = 120 ml, PTV-90 = 220 ml, RTOG PTV = 490 ml). Accordingly, the organs at risk received less irradiation dose with the proposed CTV-90 and CTV-80.
  
  
  CONCLUSIONS
  Smaller adjuvant radiotherapy CTVs targeting the high-risk local failure areas of postoperative pancreatic cancer were proposed, according to the three-dimensional spatial location of local recurrences. This may help to minimize radiation-related toxicities, achieve dose escalation, and finally reduce local recurrence.
authors.affiliation: Department of Radiation Oncology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Yu
authors.affiliation: Department of Radiation Oncology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Hu
authors.affiliation: Department of Radiation Oncology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Shui
authors.affiliation: Department of Radiation Oncology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Radiation Oncology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Chao
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Radiation Oncology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Xiaoqiu
authors.initials: X
authors.lastname: Ren
authors.affiliation: Department of Hepatobiliary and Pancreatic Surgery, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Xueli
authors.initials: X
authors.lastname: Bai
authors.affiliation: Department of Radiology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Risheng
authors.initials: R
authors.lastname: Yu
authors.affiliation: Department of Radiation Oncology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Li
authors.initials: L
authors.lastname: Shen
authors.affiliation: Department of Hepatobiliary and Pancreatic Surgery, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China.
authors.forename: Tingbo
authors.initials: T
authors.lastname: Liang
authors.affiliation: The Sidney Kimmel Comprehensive Cancer Center, the Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Department of Radiation Oncology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People's Republic of China. Qichun_Wei@zju.edu.cn.|Department of Radiation Oncology, the Second Affiliated Hospital, Ministry of Education Key Laboratory of Cancer Prevention and Intervention, Zhejiang University School of Medicine, Jiefang Road 88, Hangzhou, 310009, People's Republic of China. Qichun_Wei@zju.edu.cn.
authors.forename: Qichun
authors.initials: Q
authors.lastname: Wei
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology / Q000532:radiotherapy*; D010190:Pancreatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011184:Postoperative Period; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant; D012189:Retrospective Studies
keywords: Adjuvant radiotherapy; Local recurrence pattern; Pancreatic cancer; Spatial location; Target volume