title: Image-guided volumetric arc radiotherapy of pancreatic cancer with simultaneous integrated boost: Optimization strategies and dosimetric results.
abstract: OBJECTIVE
  To introduce volumetric modulated arc therapy treatments (VMAT) with simultaneous integrated boost (SIB) for pancreatic cancer and describe dosimetric results on a large patient series.
  
  
  METHODS
  45 patients with pancreatic malignancies were treated with 18 MV single-arc VMAT. Image guidance was performed with daily online kilo-volt cone-beam computed tomography (CBCT). The conformity index (CI) and homogeneity index (HI) to the target volumes, PTV45Gy and PTV54Gy, and dose-volume indices to OARs from the QUANTEC task group were reported. The risk of clinical nephritis was evaluated using normal tissue complication probability (NTCP). Treatments were verified in-phantom with the Delta4 system.
  
  
  RESULTS
  Average CI was 1.06 with 95% confidence intervals (95% CI) of 0.97-1.22 for PTV45Gy and 1.17 (0.66-1.61) for PTV54Gy. HI of PTV54Gy was 1.06 (1.04-1.10). OAR constraints were achieved in all patients, except for kidneys V12Gy of 48 (35.4-72.3)%. NTCP of the kidneys was 0.98 (0.6-1.7)%. Kidneys V12Gy and V20Gy were inversely related to PTV54Gy CI and maximum dose. All in-phantom tests had gamma pass rates exceeding 95% with global 3% dose difference and 3 mm distance to agreement. Patient shifts measured with CBCT had 95% CI of -0.8, +0.8 in the RL, -0.7, +0.8 in the SI, and -0.8, +0.7 cm in the AP directions.
  
  
  CONCLUSIONS
  Dosimetric results of VMAT were excellent on PTVs and organs at risk. The kidneys represent the dose-limiting organ at risk for this technique. NTCP indicates that this technique is safe from radiation-induced side effects to the kidneys.
authors.affiliation: Medical Physics Unit, Centro di Riferimento Oncologico, 33081 Aviano, Italy. Electronic address: mavanzo@cro.it.
authors.forename: Michele
authors.initials: M
authors.lastname: Avanzo
authors.affiliation: Medical Physics Unit, Centro di Riferimento Oncologico, 33081 Aviano, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Chiovati
authors.affiliation: Radiation Oncology Department, Centro di Riferimento Oncologico, 33081 Aviano, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Boz
authors.affiliation: Medical Physics Unit, Centro di Riferimento Oncologico, 33081 Aviano, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Sartor
authors.affiliation: Radiation Oncology Department, Centro di Riferimento Oncologico, 33081 Aviano, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Dozza
authors.affiliation: Medical Physics Unit, Centro di Riferimento Oncologico, 33081 Aviano, Italy.
authors.forename: Elvira
authors.initials: E
authors.lastname: Capra
mesh_terms: D054893:Cone-Beam Computed Tomography; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging; D058958:Organs at Risk; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D011336:Probability; D011786:Quality Control; D011832:Radiation Injuries / Q000517:prevention & control*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*
keywords: Cone-beam CT; Dose–volume; Image-guided; NTCP; Pancreatic; VMAT