ESTRO 37 Abstract book

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ESTRO 37

Conclusion MPMRI is useful and can influence diagnostic and therapeutic decisions in patients with biochemical relapse after radical prostatectomy. MPMRI can play an important role in radiotherapy planning as it helps to define the exact location of the relapse in the context of prostate bed, yielding to a greater precision in the definition of CTV, besides it be the premise for studies of dose escalation or descalation. EP-1603 Feasibility, dosimetric aspects and clinical results in prostatic patients: 5-years follow-up L.E. Trodella 1 , R.M. D'Angelillo 1 , M. Fiore 1 , A. Iurato 1 , A. Carnevale 1 , C. Greco 1 , A. Sicilia 1 , M. Miele 1 , P. Trecca 1 , L. Trodella 1 , S. Ramella 1 1 Campus Biomedico University, Department of Radiation Oncology, Roma, Italy Purpose or Objective Radiotherapy (RT) for prostate cancer has been constantly evolving over the last few decades, improving overall survival, cancer-specific and time progression of the disease. Different studies have shown a strong association between survival and RT doses (≥ 76 Gy). Advanced RT techniques such as modulated intensity (IMRT) and modulated intensity dynamic volumetric therapy (VMAT) facilitate and allow higher doses, minimizing the side effects of healthy surrounding tissues. Material and Methods All patients referred to our institution for radical treatment for prostate cancer have been reviewed. Dosimetric comparison between IMRT an VMAT were made to evaluate the constraints (dose limits) for the organs at risk (OARs) in the district: the rectum, the bladder, the femoral heads, and the penile bulb. In addition, toxicity was assessed (according to CTCAE version 4.02 scale), progression-free survival (PFS) and overall survival (OS). Progression disease has been evaluated from a clinical point of view, through laboratory and radiological examinations. Results From January 2010 to December 2014, a total of 261 patients with prostate cancer (including 49 at low risk, 101 at intermediate risk and 111 at high risk) were treated at our Center with radical RT for a total dose of 80 Gy (the pelvis was included in the volume of treatment in 57 patients). The minimum follow-up is 30 months. Of these, 208 were treated with IMRT technique and 53 with VMAT technique. Average age of patients was 72 years (min 42 years - max 86 years). Median PSA was 7.47 ng / ml. Dosimetric data showed that VMAT technique achieves better compliance with constraints for OARs, reducing the percentage of patients who deviate from dose limits. No patient exhibited Grade 2 Gastrointestinal (GI) and Genitourinary (GU) toxicity. 13.5% and 5.7% of patients reported, at 5 years, respectively G2 GI and G2 GU toxicity. PFS at 5 years was 82% for low and intermediate risk patients and 81% for high risk patients. At 5 years, OS of the entire population was 93.2%. OS of the population by risk class stratification, at 5 years, can be summarized as follows: at 100% low risk; in the intermediate risk of 90% and in the high risk of 93%. Conclusion Reviewing our patients with at least 5 year follow-up, we have observed low acute and late toxicity. These could support the adoption of further dose escalation mainly in high risk patients.

EP-1604 Precision of MRI-CT-image fusion based on goldmarkers for IGRT by using a phantom and clinical data D. Wegener 1 , D. Zips 1 , D. Thorwarth 2 , K. Nikolaou 3 , A. Othman 3 , U. Grosse 3 , A.C. Müller 1 1 University Hospital Tübingen, Department of Radiation Oncology, Tübingen, Germany 2 University Hospital Tübingen, Section for Biomedical Physics- Department of Radiation Oncology, Tübingen, Germany 3 University Hospital Tübingen, Department of Radiology, Tübingen, Germany Purpose or Objective To increase precision of radiation treatment (RT) delivery in prostate cancer and to reduce toxicity, MRI-based RT as well as the use of fiducials like goldmarkers (GM) have each shown promising results. However, their combined use is currently under investigation in clinical trials. Therefore, we aim to evaluate MRI-related distortions or deviations including artifacts by fiducials to estimate a A gel-phantom with two inserted GM was scanned by CT and three different MR-scanners of 1.5 T and 3 T (2mm slice thickness, T2 TSE and T1 VIBE-Dixon). After image fusion, deviations of the matches for fiducials and gel contours were measured and visibility/artifacts were evaluated. Results Visibility of GMs was shown for all modalities. The outer gel contours were matched with <1mm deviation, contour volumes varied between 0-1%. The deviations of the GMs were less than 2mm in any direction of MRI/CTand no relevant differences were found between 1,5 T and 3T MRIs. Shifts of peripherally or centrally located GM were randomly distributed. Match precision of a clinical sample including a fiducial-based MRI-CT match and consecutive MRI-match were in the same range. Conclusion In this phantom study we were able to measure small deviations of fiducial-based registrations of a reference CT with voxel-isotropic T2-TSE sequences of three different MR-scanners (1.5T and 3T). Spatial deviations of CT- and MR-contoured fiducials were less than 2mm, i.e. below the slice thickness of the applied modalities. Comparable small deviations were detectable in the clinical workflow of an example case using a MR-adaptive protocol. In addition, we were able to develop a workflow for MR-CT-image fusion and MR-only workflow. EP-1605 Outcome and toxicity in a cohort of prostate cancer patients treated with image-guided radiotherapy P. Toncheva 1 , N. Volegova-Neher 1 , K. Henne 1 , A. Grosu 1 , S. Kirste 1 1 Uniklinik Freiburg, Radiation Oncology, Freiburg, Germany Purpose or Objective Radiation therapy is an important primary treatment option in patients with prostate cancer. Fiducial marker image-guided radiotherapy allows correction of setup errors and interfraction motion resulting in improved accuracy. We aim to report outcome and toxicities of primary image-guided radiation therapy using an adaptive off-line planning protocol. potentially related bias. Material and Methods