title: Dosimetric evaluation of simultaneous integrated boost during stereotactic body radiation therapy for pancreatic cancer.
abstract: Stereotactic body radiation therapy (SBRT) provides a promising way to treat locally advanced pancreatic cancer and borderline resectable pancreatic cancer. A simultaneous integrated boost (SIB) to the region of vessel abutment or encasement during SBRT has the potential to downstage otherwise likely positive surgical margins. Despite the potential benefit of using SIB-SBRT, the ability to boost is limited by the local geometry of the organs at risk (OARs), such as stomach, duodenum, and bowel (SDB), relative to tumor. In this study, we have retrospectively replanned 20 patients with 25Gy prescribed to the planning target volume (PTV) and 33~80Gy to the boost target volume (BTV) using an SIB technique for all patients. The number of plans and patients able to satisfy a set of clinically established constraints is analyzed. The ability to boost vessels (within the gross target volume [GTV]) is shown to correlate with the overlap volume (OLV), defined to be the overlap between the GTV + a 1(OLV1)- or 2(OLV2)-cm margin with the union of SDB. Integral dose, boost dose contrast (BDC), biologically effective BDC, tumor control probability for BTV, and normal tissue complication probabilities are used to analyze the dosimetric results. More than 65% of the cases can deliver a boost to 40Gy while satisfying all OAR constraints. An OLV2 of 100cm(3) is identified as the cutoff volume: for cases with OLV2 larger than 100cm(3), it is very unlikely the case could achieve 25Gy to the PTV while successfully meeting all the OAR constraints.
authors.affiliation: Department of Radiation Oncology, Cedars Sinai Medical Center, Los Angeles, CA. Electronic address: wensha.yang@cshs.org.
authors.forename: Wensha
authors.initials: W
authors.lastname: Yang
authors.affiliation: Department of Radiation Oncology, Cedars Sinai Medical Center, Los Angeles, CA.
authors.forename: Robert
authors.initials: R
authors.lastname: Reznik
authors.affiliation: Department of Radiation Oncology, Cedars Sinai Medical Center, Los Angeles, CA.
authors.forename: Benedick A
authors.initials: BA
authors.lastname: Fraass
authors.affiliation: Department of Surgery, Cedars Sinai Medical Center, Los Angeles, CA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Nissen
authors.affiliation: Department of Gastrointestinal Oncology, Cedars Sinai Medical Center, Los Angeles, CA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Hendifar
authors.affiliation: Department of Cross-Sectional Imaging Interventional Oncology, Cedars Sinai Medical Center, Los Angeles, CA.
authors.forename: Ashley
authors.initials: A
authors.lastname: Wachsman
authors.affiliation: Department of Radiation Oncology, Cedars Sinai Medical Center, Los Angeles, CA.
authors.forename: Howard
authors.initials: H
authors.lastname: Sandler
authors.affiliation: Department of Radiation Oncology, Cedars Sinai Medical Center, Los Angeles, CA.
authors.forename: Richard
authors.initials: R
authors.lastname: Tuli
mesh_terms: D000465:Algorithms; D019583:Dose Fractionation, Radiation; D006801:Humans; D059351:Organ Sparing Treatments / Q000379:methods*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D011859:Radiography; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: Pancreas; SBRT; SIB; Simultaneously integrated boost