Helical tomotherapy of spinal chordomas: French Multicentric, retrospective study of a cohort of 30 cases.

PURPOSE: To evaluate the efficacy and toxicity of helical tomotherapy (HT) in the management of spine chordomas when proton therapy is unavailable or non-feasible. METHODS AND MATERIALS: Between 2007 and 2013, 30 patients with biopsy-proven chordomas were treated by HT in five French institutions. Information regarding local control (LC), overall survival (OS), progression-free survival (PFS) and metastasis-free survival (MFS) was collected. Clinical efficacy, toxicity and treatment quality were evaluated. RESULTS: Two-year actuarial LC, OS, PFS and MFS were 69.9%, 96.7%, 61.2% and 76.4%, respectively. HT treatments were well tolerated and no Grade 4-5 toxicities were observed. HT permitted the delivery of a mean dose of 68 Gy while respecting organ at risk (OAR) dose constraints, in particular in the spinal cord and cauda equina. CONCLUSIONS: This multicentric, retrospective study demonstrated the feasibility of HT in the treatment of spine chordomas, in the absence of hadron therapy.

Dose calculation accuracy of different image value to density tables for cone-beam CT planning in head & neck and pelvic localizations.

PURPOSE: We aimed to identify the most accurate combination of phantom and protocol for image value to density table (IVDT) on volume-modulated arc therapy (VMAT) dose calculation based on kV-Cone-beam CT imaging, for head and neck (H&N) and pelvic localizations. METHODS: Three phantoms (Catphan(®)600, CIRS(®)062M (inner phantom for head and outer phantom for body), and TomoTherapy(®) "Cheese" phantom) were used to create IVDT curves of CBCT systems with two different CBCT protocols (Standard-dose Head and Standard Pelvis). Hounsfield Unit (HU) time stability and repeatability for a single On-Board-Imager (OBI) and compatibility of two distinct devices were assessed with Catphan(®)600. Images from the anthropomorphic phantom CIRS ATOM(®) for both CT and CBCT modalities were used for VMAT dose calculation from different IVDT curves. Dosimetric indices from CT and CBCT imaging were compared. RESULTS: IVDT curves from CBCT images were highly different depending on phantom used (up to 1000 HU for high densities) and protocol applied (up to 200 HU for high densities). HU time stability was verified over seven weeks. A maximum difference of 3% on the dose calculation indices studied was found between CT and CBCT VMAT dose calculation across the two localizations using appropriate IVDT curves. One IVDT curve per localization can be established with a bi-monthly verification of IVDT-CBCT. CONCLUSIONS: The IVDT-CBCTCIRS-Head phantom with the Standard-dose Head protocol was the most accurate combination for dose calculation on H&N CBCT images. For pelvic localizations, the IVDT-CBCTCheese established with the Standard Pelvis protocol provided the best accuracy.

Use of FDG-PET to guide dose prescription heterogeneity in stereotactic body radiation therapy for lung cancers with volumetric modulated arc therapy: a feasibility study.

BACKGROUND: The aim of this study was to assess if FDG-PET could guide dose prescription heterogeneity and decrease arbitrary location of hotspots in SBRT. METHODS: For three patients with stage I lung cancer, a CT-simulation and a FDG-PET were registered to define respectively the PTVCT and the biological target volume (BTV). Two plans involving volumetric modulated arc therapy (VMAT) and simultaneous integrated boost (SIB) were calculated. The first plan delivered 4 × 12 Gy within the PTV(CT) and the second plan, with SIB, 4 × 12 Gy and 13.8 Gy (115% of the prescribed dose) within the PTV(CT) and the BTV respectively. The Dmax-PTV(CT) had to be inferior to 60 Gy (125% of the prescribed dose). Plans were evaluated through the D95%, D99% and Dmax-PTV(CT), the D2 cm, the R50% and R100% and the dice similarity coefficient (DSC) between the isodose 115% and BTV. DSC allows verifying the location of the 115% isodose (ideal value = 1). RESULTS: The mean PTV(CT) and BTV were 36.7 (±12.5) and 6.5 (±2.2) cm3 respectively. Both plans led to similar target coverage, same doses to the OARs and equivalent fall-off of the dose outside the PTV(CT). On the other hand, the location of hotspots, evaluated through the DSC, was improved for the SIB plans with a mean DSC of 0.31 and 0.45 for the first and the second plans respectively. CONCLUSIONS: Use of PET to decrease arbitrary location of hotspots is feasible with VMAT and SIB for lung cancer.

High-dose pre-operative helical tomotherapy (54 Gy) for retroperitoneal liposarcoma.

PURPOSE: To evaluate the feasibility of pre-operative radiotherapy (54 Gy) with Helical Tomotherapy (HT) followed by surgery. METHODS AND MATERIALS: Ten patients with non-metastatic resectable retroperitoneal liposarcomas were treated by pre-operative tomotherapy (54 Gy) and surgery. Clinical and biological toxicities were evaluated on the CTCAEV3.0 scale. For nine patients, delivered tomotherapy plans were compared with retrospectively-planned dynamic intensity-modulated radiotherapy (IMRT) dosimetric studies. RESULTS: No immediate or late Grade>2 toxicities were observed after radiotherapy. Post-operatively, one patient died and three patients experienced Grade 3 toxicity (two digestive and one metabolic). These toxicities disappeared and only two patients presented persistent Grade 1 paresthesia. R0 resection was obtained for four patients, R1 for four, and R2 resection for two. With a median follow-up of 26 months, no local or metastatic relapse was observed. Dosimetric comparisons between HT and retrospectively-planned IMRT demonstrate adequate target volume coverage for both techniques. Gastrointestinal sparing is higher with HT with a D200cc reduced by 5 Gy. Integral dose (ID) was increased in HT. CONCLUSIONS: High dose pre-operative radiotherapy (54 Gy) for retroperitoneal liposarcoma is feasible and mostly well tolerated. Cumulative toxicity and tolerance depend mainly on patient's general status. Image-guided radiation therapy (IGRT) is essential, irrespective of the IMRT technique used. Furthermore, HT offers the possibility of sparing selected areas in such complex volumes.