EP-1401: First experience with Elekta Flattening Filter Free beams for stereotactic irradiation of brain metastases

EP-1401: First experience with Elekta Flattening Filter Free beams for stereotactic irradiation of brain metastases

S122 ESTRO 33, 2014 1 Peter MacCallum Cancer Centre, Radiotherapy Services, Melbourn Victoria, Australia Peter MacCallum Cancer Centre, Department ...

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ESTRO 33, 2014


Peter MacCallum Cancer Centre, Radiotherapy Services, Melbourn Victoria, Australia Peter MacCallum Cancer Centre, Department of Physical Sciences, Melbourn Victoria, Australia 3 Peter MacCallum Cancer Centre, Division of Cancer Imaging and Radiation Oncology, Melbourn Victoria, Australia 2

Purpose/Objective: Optimal 3D conformal planning techniques are yet to be defined in the context stereotactic ablative body radiotherapy (SABR) for primary renal cell carcinoma (RCC). The purpose of this study is to determine typical features of treatment planning techniques used at our institution and evaluate outcomes to these techniques in terms of early toxicity and renal impairment. Materials and Methods: This was an interim analysis of a prospective clinical trial of SABR for primary RCC. A prescription of 26Gyin 1 fraction is used for tumours of < 5cm in size and 42Gy in 3 fractions for tumours of > 5cm in size, prescribed to the covering isodose (70-80% of DMax). Maximum intensity projection (MIP) datasets from a planning 4DCT were used to define the internal target volume (ITV) with a 5mm planning target volume (PTV) margin applied. A minimum number of 6 fields were allowed, with99% of the PTV to receive the full prescription dose calculated using anAnisotropic Analytical Algorithm (Type B). Assessment of RTOG defined intermediate dose conformity index (R50%) was derived from the formula R50%=(volume of 50%prescription dose)/(PTV Volume). Early toxicities were defined as toxicities recorded using CTCAE v4.0 criteria within 3 months of SABR. Renal function was measured through Cr-51 EDTA GFR and serum electrolytes/creatinine at baseline and 70 days post SABR. Results: From July 2012 to August 2013, a total of 20 patients were enrolled (15 males and 5 females). The mean age was 73.6 years. The mean tumour size was 4.8cm (range 2.0-7.5cm),with 11 patients receiving 26Gy/1 and and 9 patients receiving 42Gy/3 SABR. The median number of beams was 9 (range 6-13), with median of 6 co-planar and 3non-coplanar beams. While 6MV photons were the predominant radiation energy used, 18MV photons were used for several patients to reduce skin dose. The mean PTV was 123.3 cc,(range 22.7-273.6 cc). An increasing PTV volume correlated with an increase in the number of beams used (r = 0.608, p= 0.004). The mean R50% was 4.06 (range 2.75), which was inversely correlated to increasing PTV volume (r = -0.624, p < 0.003). No grade 3 or grade 4 toxicities were recorded; 5/20 patients (25%) sustained grade 2 toxicities, 8/20 (40%)patients had grade 1 toxicities, and 7/20 (35%) of patients were asymptomatic from treatment. There was no significant change from mean baseline GFR DVH parameters QC Efficiency Brain Delivery Eye_RV10 Arc 1 Brainstem Arc 2 time Patient: Dose(Gy)Plan (Gy) 1: 15 6MV 0.12 FFF 0.10 2: 18 6MV 7.46 FFF 6.98 3: 24 6MV 2.21 FFF 1.99 4: 24 6MV 3.14 FFF 2.88 5: 24 6MV 1.92 FFF 2.31 average 6MV2.97 FFF 2.85

OptNrv_R (Gy) (Gy) 0.11 0.19 0.10 0.17 0.14 0.28 0.09 0.18 0.53 0.46 0.65 0.49 1.88 0.98 2.10 1.12 2.15 2.21 1.55 1.58 0.96 0.83 0.90 0.71

(Gy) (passrate)(passrate)(s) 45.25 100% 93% 485 42.88 99% 93% 189 23.98 100% 99% 496 23.44 100% 98% 205 16.24 100% 96% 711 15.64 99% 99% 294 17.82 100% 97% 610 16.94 100% 99% 200 6.68 91% 96% 664 6.81 100% 96% 288 21.99 98% 96% 593 21.14 100% 97% 235

Table 1. DVH parameters of OAR (Dmax, volume of the 10Gy isodose), QC passrates and (estimated) delivery times for regular 6MV and 6MV FFF plans of five patients. Tolerances for brainstem, optic nerve and eye are 12Gy, 8Gy and 4Gy, respectively. to70-day GFR (62 mls/min versus 54mls/min, p= 0.571), nor mean baseline creatinine to 70-day creatinine (108 ul/mol vs 118 ul/mol, p= 0.276).

Conclusions: The 3D conformal SABR technique at our institution involved on average 6 coplanar and 3 non-coplanar beams, with an average R50% conformity index of 4.06. Despite the treatment of large volume targets, this technique was associated with a low rate of toxicity within 3 months and minimal early decline of renal function. Longerterm follow-up is ongoing in this patient cohort. EP-1401 First experience with Elekta Flattening Filter Free beams for stereotactic irradiation of brain metastases E. Lamers-Kuijper1, G. Franssen1, A. Mourik van1, T. Perik1, L. Dewit1, A. Wolff1, C. Vliet van-Vroegindeweij1, E. Damen1 1 The Netherlands Cancer Institute, Radiotherapy Department, Amsterdam, The Netherlands Purpose/Objective: In June 2013, the Flattening Filter Free beam of the Elekta Versa HD linac was introduced clinically at our department. The aim of this study is to compare 6MVFFF treatment with standard 6MV treatment for stereotactic radiotherapy of brain metastasis in terms of dose distributions, quality control (QC) and treatment efficiency. Materials and Methods: Five patients with small, single lesions (PTV 1.53.6 cm) were reviewed. For each patient, clinically acceptable 6MV FFF and regular 6MV plans were made. A dual, noncoplanar arc VMATtechnique was used, with gantry angles depended on the location of the target. Treatment plans for the Elekta Agility MLC (5 mm leaves) were made using the Pinnacle3treatment planning system v9.6. Single fraction dose (15Gy, 18Gy or 24 Gy, depending on the diameter of the PTV) was prescribed such that the prescription isodose encompassed at least 95% of the PTV. The maximum dose was restricted to150% of the prescription dose. Dose distributions were verified at the isocenter plane with the PTW Octavius 2D phantom in combination with the PTW1000SRS detector array. A 2%/2mm gamma evaluation (local dose) was performed on calculated and measured dose. Pass rates were defined as the percentage of measured points within the 30% isodose line with gamma <1. Currently, total treatment times for single lesion brain metastases are usually around 20-25 minutes, including patient setup, sophisticated position verification. Results: Plans created with FFF generally resulted in slightly lower OAR doses (see table 1;DVH parameters). QC of the treatment plans was excellent and comparable for 6MV and FFF (see table 1; QC). Due to the much higher dose rate of the FFF beam, the estimated delivery time decreased with approximately a factor 2.5 compared to the plan without FFF (see table 1; Efficiency). Conclusions: The quality of FFF plans for stereotactic treatment of brain metastases is at least equivalent to regular 6MV plans in terms of dose

ESTRO 33, 2014 distribution and QC. With regard to treatment efficiency, the reduction in delivery time is the main advantage and especially beneficial when treating multiple lesions. Based on these initial experiences, we extended the use of FFF to multiple brain metastases and will investigate whether treatment can be performed in shorter timeslots to reduce treatment costs. EP-1402 Feasibility of SBRT with VMAT and high intensity photon beams for hepatocellular carcinoma patients P. Wang1, W.C. Hsu1, N.N. Chung1, F.L. Chang1, C.J. Jang1, A. Fogliata2, G. Nicolini2, E. Vanetti2, A. Clivio2, L. Cozzi2 1 Cheng-Ching General Hospital, Radiation Oncology, Taichung, Taiwan 2 Oncology Institute of Southern Switzerland, Medical Physics, Bellinzona, Switzerland Purpose/Objective: To report technical features, early outcome and toxicity of stereotactic body radiation therapy (SBRT) treatments with volumetric modulated arc therapy (RapidArc) for patients with hepatocellular carcinoma (HCC). Materials and Methods: Twenty patients (22 lesions) were prospectively enrolled in a feasibility study. Dose prescription was 50Gy in 10 fractions. Seven patients (35%) were classified as AJCC stage I-II while 13 (65%) were stages III-IV. Eighteen patients (90%) were Child-Pugh stage A, the remaining were stage B. All patients were treated with RapidArc technique with flattening filter free (FFF) photon beams of 10MV from a TrueBeam linear accelerator. Technical, dosimetric and early clinical assessment was performed to characterize treatment and its potential outcome. Results: Median age was 68 years, median initial tumor volume was 124cm3 (range: 6- 848). Median follow-up time was 7.4 months (range: 313). All patients completed treatment without interruption. Mean actuarial overall survival was of 9.6±0.9 months (95%C.L. 7.8-11.4), median survival was not reached; complete response was observed in 8/22 (36.4%) lesions; partial response in 7/22 (31.8%), stable disease in 6/22 (27.3%), 1/22 (4.4%) showed progression. Toxicity was mild with only 1 case of grade 3 RILD and all other types were not greater than grade 2. Concerning dosimetric data, Paddick conformity index was 0.98±0.02; gradient index was 3.82±0.93; V95% to the clinical target volume was 93.6±7.7%. Mean dose to kidneys resulted lower than 3.0Gy; mean dose to stomach 4.5±3.0Gy; D1cm3 to spinal cord was 8.2±4.5Gy; D1% to the esophagus was 10.2±9.7Gy. Average beam on time resulted 0.7±0.2 minutes (range: 0.4-1.4) with the delivery of an average of 4.4 partial arcs (range: 3-6) of those 86% non-coplanar.

Conclusions: Clinical results could suggest to introduce VMAT-RapidArc as an appropriate SBRT technique for patients with HCC in view of a prospective dose escalation trial. EP-1403 Inoperable colorectal liver metastases: A monoinstitutional experience and preliminary outcome of SABR M. Scorsetti1, T. Comito1, L. Cozzi2, A. Tozzi1, C. Iftode1, P. Navarria1, E. Clerici1, P. Mancosu1, F. Lobefalo1, S. Tomatis1 1 Humanitas Clinical and Research Center, Radiotherapy and Radiosurgery, Rozzano (Milan), Italy 2 Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, Switzerland Purpose/Objective: To evaluate the feasibility and efficacy of Stereotactic Ablative Body Radiotherapy (SABR) in the treatment of colorectal liver metastases.

S123 Materials and Methods: A prospective phase II trial on patients with inoperable liver metastases, not amenable to other locoregional therapies, started in February 2010 at our Institution. Inclusion criteria were: Karnofsky Performance Status of 70; no evidence of progressive or untreated gross disease outside the liver; maximum tumor diameter less than 6 cm; no more than 3 liver lesions; normal liver volume greater than 1000 cm3; adequate liver function. Forty-two patients with colorectal liver metastases not amenable to surgery or radiofrequency ablation (RFA), were treated with SABR for a total number of 52 lesions. Dose prescription was 75 Gy in 3 consecutive fractions, delivered with RapidArc VMAT, with 10MV FFF photons. Mean size of the lesions was 3.5 cm (range 1.1–5.4). Toxicity was classified according to the Common Toxicity Criteria (CTC) version 3.0. Results: Median follow-up was 20 (range 4–41) months. In field progression was observed in four patients for a total of 4 lesions. Twelve, 20 and 24 months actuarial local control (LC) rate was 95%, 93% and 90%, respectively. A subgroup analysis for lesion diameter > 3 cm compared with smaller metastases revealed no significantly increased risk of local recurrence (p=0.92). Median overall survival (OS) was 20.5 months. Actuarial OS rate at 12, 20 and 24 months was 83%, 70% and 66%, respectively. Univariate analysis of the main prognostic factors showed a statistically significant decrease of OS for cumulative GTV bigger than 3 cm (p= 0.01). Median progression-free survival (PFS) was 9 months. No patients experienced radiation-induced liver disease (RILD) or grade >3 toxicity. Conclusions: SABR is a safe and non-invasive alternative for the treatment of inoperable colorectal liver metastases, showing optimal local control and promising survival rate. EP-1404 Malignant lung nodules treated with Stereotactic Body Radiotherapy (SBRT): A single institution experience P. Borghetti1, M. Maddalo2, P. Vitali1, F. Trevisan2, B. Bonetti1, M. Buglione2, N. Pasinetti1, F. Barbera1, S.M. Magrini2 1 Spedali Civili Brescia, Radiation Oncology, Brescia, Italy 2 Brescia University, Radiation Oncology, Brescia, Italy Purpose/Objective: To retrospectively evaluate efficacy and toxicity of SBRT in the management of primary or recurrent/metastatic malignant lung nodules. Materials and Methods: Data of all patients (pts) treated with lung SBRT were reviewed. Local Control (LC) and acute (AT) and late (LT) toxicity rates were the endpoints of the analysis. Results: From 07/2011 to 07/2013 28 pts were treated. Median age was 74 years (range: 42-89) with 20/28 pts aged more than 70 years. Median follow-up was 10 months (range 2-22). 18 pts had a primary lung cancer, 6 pts presented recurrences or metastases from lung cancer, 4 pts had metastases from other sites (1 thyroid,1 breast, 2 colo-rectal). All pts with a primary lung cancer were surgically inoperable because of comorbidity, 10/18 presented chronic obstructive pulmonary disease staged from moderate to very severe (GOLD classification). Diagnosis was radiological in 18 pts and both histological and radiological in 10 pts.All pts were staged with contrast-enhanced CT scan, 25 had also a FDG-PET/CT. The number of lesions treated with SBRT was 1 in 23 pts, 2 in 3 pts, 3 and 4 in 1 patient. For planning data acquisition pts were positioned supine with arms above the head and immobilised with a diaphragmatic compression. A 3 mm slice-4D CT scan was obtained using a fast multi-slice scanner correlated to the respiratory cycle to create a composite GTV (ITV) including all positions of the target. PTV volume, obtained by expansion from ITV to CTV (3-6 mm) and from CTV to PTV (3-6mm), ranged from 11 to 177 cc. The RT-technique was Tomotherapy, VMAT or arc-conformed therapy in 5, 25 and 7 pts respectively, with daily IGRT control. The fractionation schedule was 55 Gy in 5 fractions in 22 pts and 52 Gy in 8 fractions in 6 pts. G3 lung AT rate was 14% (4 pts had steroids for clinical and radiological evidences of acute pneumonitis). G3-G4 lung LT rate (recorded only for pts with a minimum follow-up of 6 months) was 11% (2 pts with severe symptomatic fibrosis and dense radiographic changes and 1 patient required intensification of continuous oxygen therapy). The patient with 4 lesions (PTV cumulative volume of 177cc) had G3 lung AT and LT and the worst lung-DVH of the series. No severe AT or LT of oesophagus, heart, brachial plexus or bone (rib cage) was observed. 1-year overall survival was 79%. One patient died for disease progression (mediastinal involvement) and 2 pts died for other causes. 1-year LC was 91%, with only 2 disease progression at the SBRT site. Among pts with primary lung cancer 1-year progression free survival (PFS) was 78%, with 2 mediastinal and 1 systemic recurrence.