Abstract Book

S863

ESTRO 37

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

Results The MPMRI was positive for macroscopic relapse in 36.36% (4 pts), PSA values at the time of biochemical recurrence varied from 0.15 ng/ml to 0.53 ng/ml and PSADT varied from 6 months up to >12 months. In 1 pt MPMRI showed, at the level of bladder-uretral anastomosis, a vegetative tissue thickening in the bladder lumen which was later histologically confirmed to be normal prostatic tissue, so no SRT was planned and the value of PSA (0,15 ng/ml) remained stable. MPMRI was negative for macroscopic recurrence in 45.45% (5 pts), therefore we performed standard SRT at prostate bed (PSA values at the time of biochemical recurrence also ranged from 0.15 ng/ml to 0.46 ng/ml and PSADT varied from 3 to 12 months).In another pt MPMRI detected a dubious macroscopic recurrence in the prostate bed and a femoral head metastasis, subsequently not confirmed by PET choline, so SRT was performed as standard. The value of PSA at time of biochemical recurrence was 0.26 ng/ml. The mean volumes of intersection between rectum and HR- PTV were smaller than the mean intersection volumes of the rectum and Standard PTV (p=0.0166). The same occurred for the mean volumes of intersection between bladder and HR PTV than bladder and Standard PTV (p=0.0119). No cases of acute toxicity were reported in the two groups.

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