Image-guided volumetric arc radiotherapy of pancreatic cancer with simultaneous integrated boost: Optimization strategies and dosimetric results

Michele Avanzo, Paola Chiovati, Giovanni Boz, Giovanna Sartor, Francesca Dozza, Elvira Capra

Research output: Contribution to journalArticle

Abstract

Purpose: 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 and materials: 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.

Original languageEnglish
Pages (from-to)169-175
Number of pages7
JournalPhysica Medica
DOIs
Publication statusPublished - 2016

Keywords

  • Cone-beam CT
  • Dose-volume
  • Image-guided
  • NTCP
  • Pancreatic
  • VMAT

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging
  • Physics and Astronomy(all)

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