title: Linac-based extracranial radiosurgery with Elekta volumetric modulated arc therapy and an anatomy-based treatment planning system: Feasibility and initial experience.
abstract: We reported our initial experience in using Elekta volumetric modulated arc therapy (VMAT) and an anatomy-based treatment planning system (TPS) for single high-dose radiosurgery (SRS-VMAT) of liver metastases. This study included a cohort of 12 patients treated with a 26-Gy single fraction. Single-arc VMAT plans were generated with Ergo++ TPS. The prescription isodose surface (IDS) was selected to fulfill the 2 following criteria: 95% of planning target volume (PTV) reached 100% of the prescription dose and 99% of PTV reached a minimum of 90% of prescription dose. A 1-mm multileaf collimator (MLC) block margin was added around the PTV. For a comparison of dose distributions with literature data, several conformity indexes (conformity index [CI], conformation number [CN], and gradient index [GI]) were calculated. Treatment efficiency and pretreatment dosimetric verification were assessed. Early clinical data were also reported. Our results reported that target and organ-at-risk objectives were met for all patients. Mean and maximum doses to PTVs were on average 112.9% and 121.5% of prescribed dose, respectively. A very high degree of dose conformity was obtained, with CI, CN, and GI average values equal to 1.29, 0.80, and 3.63, respectively. The beam-on-time was on average 9.3 minutes, i.e., 0.36min/Gy. The mean number of monitor units was 3162, i.e., 121.6MU/Gy. Pretreatment verification (3%-3mm) showed an optimal agreement with calculated values; mean γ value was 0.27 and 98.2% of measured points resulted with γ < 1. With a median follow-up of 16 months complete response was observed in 12/14 (86%) lesions; partial response was observed in 2/14 (14%) lesions. No radiation-induced liver disease (RILD) was observed in any patients as well no duodenal ulceration or esophagitis or gastric hemorrhage. In conclusion, this analysis demonstrated the feasibility and the appropriateness of high-dose single-fraction SRS-VMAT in liver metastases performed with Elekta VMAT and Ergo++ TPS. Preliminary clinical outcomes showed a high rate of local control and minimum incidence of acute toxicity.
authors.affiliation: Medical Physics Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Università Cattolica del Sacro Cuore, Campobasso, Italy. Electronic address: savinocilla@gmail.com.
authors.forename: Savino
authors.initials: S
authors.lastname: Cilla
authors.affiliation: Radiotherapy Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Università Cattolica del Sacro Cuore, Campobasso, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Deodato
authors.affiliation: Radiotherapy Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Università Cattolica del Sacro Cuore, Campobasso, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Macchia
authors.affiliation: Radiotherapy Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Università Cattolica del Sacro Cuore, Campobasso, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Digesù
authors.affiliation: Medical Physics Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Università Cattolica del Sacro Cuore, Campobasso, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Ianiro
authors.affiliation: Medical Physics Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Università Cattolica del Sacro Cuore, Campobasso, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Viola
authors.affiliation: Medical Physics Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Università Cattolica del Sacro Cuore, Campobasso, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Craus
authors.affiliation: Radiotherapy Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Università Cattolica del Sacro Cuore, Campobasso, Italy; Radiation Oncology Unit, Policlinico Universitario "A. Gemelli", Università Cattolica del Sacro Cuore, Roma, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Valentini
authors.affiliation: Medical Physics Unit, Policlinico Universitario "A. Gemelli", Università Cattolica del Sacro Cuore, Roma, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Piermattei
authors.affiliation: Radiation Oncology Unit, Department of Experimental, Diagnostic and Specialty Medicine-DIMES, S. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
authors.forename: Alessio G
authors.initials: AG
authors.lastname: Morganti
mesh_terms: D006801:Humans; D008113:Liver Neoplasms / Q000532:radiotherapy* / Q000556:secondary*; D058958:Organs at Risk; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*
keywords: Liver; Metastases; SBRT; VMAT