ESTRO 37 Abstract book

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ESTRO 37

ablative stereotactic body radiotherapy (SBRT). This study aims to assess in a prospective manner the impact of [18F]Choline ([18F]FMCH) PET/CT guided SBRT in patients with oligometastatic PCa. Material and Methods Between May 2011 and December 2016, 53 patients with oligometastatic PCa (defined as ≤3 synchronous active lesions detected with [18F]FMCHPET/CT) out of 98 patients with biochemical relapse of PCa were enrolled in the present prospective clinical trial. All patients were treated with salvage SBRT until the occurrence of a multimetastatic disease (>3 active synchronous metastases). Primary endpoint analyzed was the length between the baseline PET/CT and the beginning of systemic therapy. Results A total of 85 lesions were treated with SBRT. After a median follow-up of 20.3 months, 32 pts started systemic therapy after 39.7 months from the first PET/CT whereas 23 did not. Toxicity related to SBRT greater than G2 where not recorded. Results of semiquantitative parameters and texture features analysis are under Salvage [18F]FMCHPET/CT-guided SBRT is feasible, well tolerated and succeeded in deferring the initiation of systemic therapy in selected patients with oligometastatic PCa. EP-1589 VMAT SBRT For Localized Prostate Cancer: 4- Year Follow-Up And Correlation With WHO2016 Grade Groups G.R. D'Agostino 1 , L. Di Brina 1 , C. Franzese 1 , D. Franceschini 1 , E. Clerici 1 , S. Tomatis 1 , C. Iftode 1 , A. Tozzi 1 , P. Navarria 1 , F. De Rose 1 , T. Comito 1 , M. Scorsetti 1 1 Istituto Clinico Humanitas, Radiotherapy and Radiosurgery, Rozzano Milan, Italy Purpose or Objective This study updates our previously reported experience on the efficacy and toxicity of a Linac-based stereotactic body radiotherapy (SBRT) in patients with low or intermediate risk prostate cancer, exploring the potential correlation between biochemical free survival and the WHO 2016 prostate cancer Grading System. Material and Methods Biopsy confirmed prostate cancer patients were enrolled, provided that they had the following characteristics: initial PSA <20ng/ml, Gleason Score <8, IPSS <8. The treatment schedule was 35 Gy in 5 fractions, delivered every other day, with volumetric modulated arcs and flattening filter free beams. Toxicity was recorded according to CT-CAE criteria v3.0. Biochemical failure was calculated according to the Phoenix definition. Results Between February 2011 and March 2015, 90 patients were enrolled (53 low risk, 37 intermediate risk, NCCN criteria). The median age was 71 years (range 48–82). The median initial PSA was 6.98 ng/ml (mean 7.18, range 2.7–17.0). According to the WHO 2016 Grading System 57 patients (63.3%) were Grade Group (GG) 1, 22 patients (24.5%) were GG 2 and 11 patients (12.2%) GG 3. Acute toxicity was mild, with 32.2 patients presenting a G1 urinary toxicity and 32.2% of patients presenting a G2 urinary toxicity, mainly represented by urgency, dysuria and stranguria. A rectal G1 toxicity was found in a 15.5% of patients, while a rectal G2-toxicity was recorded in 6.6% of patients.. Urinary late toxicity was G1 in 48.9% of cases, G2 in 2.2%. A G1 late proctitis was recorded in evaluation. Conclusion

18.0 % of patients. At a median follow up of 48 months (range 10-67) all patient are still alive. Four-year BFS was 97.7 % for GG 1 patients, 95.0% for GG 2 patients, 72.9% for GG 3 patients (p 0.028). Four biochemical failures were recorded (GG 1: 1 case, GG 2: 1 case, GG 3: 2 cases). Pet-Choline revealed a local recurrence (GG1), 2 cases of distant metastases (GG2: 1, GG3:1), 1 case with both local recurrence and bone metastasis (GG3). Cox regression analysis showed an HR of 3.67 (95% C.I. 1.07- 12.55, p 0.037) of biochemical failure for GG3 patients compared to GG1 and GG2. Conclusion After a 4-year follow-up our analysis suggests that SBRT may be considered as a valid therapeutic option for low- and intermediate risk prostate cancer patients, warranting an adequate control of disease, with mild toxicity profiles. It also confirms that among the intermediate risk patients, those with a GG 3 disease bear a worse prognosis and are at major risk of biochemical failure after SBRT. EP-1590 PSA kinetics in prostate cancer patients after SBRT radiotherapy using CyberKnife - updated data. M. Konkol 1 , P. Milecki 1 , A. Skrobała 2 , A. Jodda 2 1 Greater Poland Cancer Centre, Oddzial Radioterapii I I Radiotherapy Dept., Poznan, Poland 2 Greater Poland Cancer Centre, Department of Medical Physics, Poznan, Poland Purpose or Objective The aim of the study was to assess the kinetics of the Prostate-Specific Antigen (PSA) in prostate cancer patients after stereotactic body radiotherapy using CyberKnife system in 24-months follow-up. Material and Methods 44 localized prostate adenocarcinoma patients (33 low and 11 intermediate risk) without hormonal therapy, were irradiated using the CyberKnife Radiosurgical System. The prescription dose was 36,25 Gy in five fractions. During the 2-year follow-up all the patients had at least eight PSA measurements – before the treatment (1-2 months before), during RT (after the 4 th fraction) and 1, 3, 6, 12, 18 and 24 months after RT. Additional measurements were made if necessary. Results The mean initial PSA value among the patients was 6,25 ng/ml (range from 3,02 to 17,46 ng/ml). During the treatment, we observe the PSA increase – the mean value 11,89 ng/ml (4,13-30,68ng/ml, 155% of the initial PSA in average). In 14 cases we noticed the PSA nadir 12 months after the treatment. The rest of the patients achieved their nadirs after 24 months with a mean value of 0,80 ng/ml (0,10- 3,21 ng/ml). The mean slope of the PSA was 0,56 ng/ml/month (median 0,46 ng/ml/month). In 10 cases we observed PSA bounce (3 of them met a biochemical failure criteria). No true biochemical failure was observed. Conclusion The PSA kinetics after treatment can reflect the biological effect of radiation on prostate cancer and potentially correlate with a clinical outcome. Especially the lower value of PSA nadir (<0,5 ng/ml) is considered to associate with an increased freedom from biochemical failure. The interpretation of PSA slope is more controversial however some studies indicates a correlation with clinical outcome. What is more we need to remember about a typical PSA bounce (similar to brachytherapy) which can mimic a biochemical failure. It is also probable that some patients will achieve a nadir