ESTRO 36 Abstract Book

S724 ESTRO 36 _______________________________________________________________________________________________

Francolini 2 , I. Meattini 2 , M. Mangoni 2 , S. Scoccianti 2 , L. Livi 2 1 Azienda Ospedaliera Universitaria Careggi, Radiotherapy Unit, Firenze, Italy 2 Universita degli Studi di Firenze, Radiotherapy Department, Florence, Italy 3 IFCA, Radiotherapy Department, Florence, Italy Purpose or Objective Biochemical recurrence can occur following definitive external beam radiation therapy (EBRT) for localized prostate cancer. Focal robotic stereotactic body radiotherapy (rSBRT) to the recurrent intraprostatic tumor is emerging as a valuable option in this setting. In this retrospective study we evaluated efficacy and toxicity of robotic SBRT for exclusive local failure after primary EBRT. Material and Methods Data from 28 patients treated at our Institution from September 2012 to December 2015 with rSBRT for prostate cancer recurrence after definitive EBRT were retrospectively reviewed. Local intraprostatic recurrence was assessed by 18 F-choline positron emission tomography– computed tomography (PET); a dose of 30 Gy was delivered in 5 fractions. PSA was assessed at 2 months, 6 months, and every 3 months following rSBRT. Toxicity was assessed by the Common Terminology Criteria for Adverse Events toxicity scale (CTCAE v.4.03). Results Patients were stratified in low (5, 17.9%), intermediate (9, 32.1%) and high risk group (14, 50.0 %) at diagnosis. Median patient age at rSBRT was 78.5 (62-86) years. All patients received prior EBRT for a median total dose of 76 Gy (62- 80 Gy) in 2 (1.8-3.1) Gy/fraction. Median time from primary treatment to relapse was 74.1 (19.3-149.2) months. Five patients were receiving androgen deprivation (AD) following prior biochemical failure; median pre-treatment PSA value was 2.7 (2.1-14.4) ng/ml. Twenty-five patients showed biochemical response to treatment at 2 and 6 months, median PSA decline -54.0% (2.2-95.0) and -76.0% (35.9-95.0%) respectively; three patients experienced early PSA progression at 2 and 6 months, median PSA elevation +112.3% (20.0-204.5%) and +267.0% (41.9-309.1%), respectively. At the time of our analysis, after a median follow-up of 20.9 (6.3-49.2) months, 10 patients showed no evidence of disease, 2 patients pursued AD with stable PSA levels, while 10 patients experienced biochemical relapse; among them, metastatic recurrence occurred in 4 cases. Biochemical Progression-Free Survival (bPFS) was 96.4% and 75.0% at 12 and 18 months, respectively. Rectal and bladder acute toxicity grade 1-2 was found in 4 and 1 cases, respectively ; grade 1-2 late rectal and bladder toxicity occurred in 1 and 7 cases, respectively. One patient experienced both grade 3 acute and chronic bladder toxicity, consisting of acute urinary retention and hematuria respectively. At univariate and multivariate analysis of pre-treatment variables, impaired bPFS was correlated only with high risk category at diagnosis (HR:13.06, p=0.021). No predictive factor for improved bPFS was found at subset analysis in responding patients, though a trend was observed for PSA decline at 6 months >76.0% (p=0.06). Conclusion Focal rSBRT can achieve long-lasting remission and delay initiation of medical treatment,in particular in low/intermediate risk patients at diagnosis, with acceptable incidence of acute and late toxicity. EP-1352 Single-fraction stereotactic body radiotherapy for nodal oligorecurrent prostate cancer M. Loi 1 , G. Simontacchi 2 , B. Detti 2 , V. Di Cataldo 3 , P. Bonomo 2 , L. Masi 3 , R. Doro 3 , I. Bonucci 3 , S. Cipressi 3 , I. Desideri 2 , D. Greto 2 , C. Becherini 2 , C. Delli Paoli 2 , R.

EP-1350 Stereotactic re-irradiation for prostate cancer recurrence after upfront surgery and radiotherapy V. Di Cataldo 1 , G. Simontacchi 2 , B. Detti 2 , M. Loi 2 , P. Bonomo 2 , L. Masi 1 , R. Doro 1 , I. Bonucci 1 , S. Cipressi 1 , D. Greto 2 , M. Mangoni 2 , I. Desideri 2 , I. Meattini 2 , S. Scoccianti 2 , E. Olmetto 2 , C. Muntoni 2 , G.A. Carta 2 , L. Livi 2 1 IFCA, Department of Radiotherapy, Firenze, Italy 2 University of Florence, Radiation Therapy Department, Florence, Italy Purpose or Objective Recurrence of prostatic cancer after radical prostatectomy and external-beam radiation therapy (EBRT) is a common occurrence in daily clinical practice. We present our experience of re-irradiation with robotic stereotactic body radiation therapy (rSBRT) for isolated recurrence in the prostatic bed from prostate cancer previously treated with surgery and radiation therapy. Material and Methods Between June 2012 and February 2016, rSBRT was administered for isolated local relapse to 22 patients previously treated with prostatectomy and adjuvant (9, 40.1%) or salvage (13, 59.9%) EBRT. After primary treatment, all patients experienced a biochemical recurrence with an isolated relapse in the prostatic bed diagnosed with 18F-choline positron emission tomography– computed tomography (PET) with or without pelvic magnetic resonance (MRI). The gross tumor volume (GTV) was defined on the basis of clinical and radiological findings by image fusion of PET and/or MRI. The total dose was 30 Gy in 5 fractions prescribed to the 80% isodose line. PSA was assessed at 2, 6 and every 3 months, following rSBRT. Toxicity was assessed by the Common Terminology Criteria for Adverse Events toxicity scale (CTCAE v.4.03). Results Twenty-two patients were treated and followed for a median time of 19.5 months (range: 59,4-74.0 months). Prior EBRT had a median total dose of 68 Gy (range 59,4- 74.0 Gy ) in 1,8-2 Gy for fraction. Median time from EBRT to relapse was 73,3 months (range: 16,9-203.1). Seven patients were receiving androgen deprivation therapy (ADT) following prior biochemical failure; median pre-re- irradiation PSA value was 1.9 ng/ml (0,4-30). Eighteen patients had biochemical response at 2 and 6 months, with a median PSA decrease of 44,9% and 64,9% respectively; four patients experienced early PSA progression at 2 and 6 months, the median PSA rise was 85,1% and 228,6% respectively. At the time of our analysis, 10 patients showed no evidence of disease, in 2 patients an hormonal treatment was continued with stable PSA levels, while 10 patients had biochemical relapse and four of these had metastatic disease. Biological Progression-free Survival (bPFS) was 81.8% and 68.2% at 6 and 12 months, respectively. Treatment was well tolerated, genitourinary acute and late G1-G2 toxicity occurred in 6 and 5 patients respectively, while two patients experienced late rectal G1-G2 toxicity. At univariate and multivariate analysis of pre-treatment variables, impaired biochemical relapse- free survival (BRFS) was correlated with the use of ADT at the moment of the treatment (p=0.013). Subset analysis in responding patients did not found predictor of BRFS. Conclusion RSBRT for isolated recurrence in the prostatic bed from prostate cancer previously treated with prostatectomy and EBRT showed favourable results in biochemical control with low and acceptable toxicity, however further prospective studies are needed to confirm these results. EP-1351 Stereotactic radiotherapy in recurrent prostate cancer previously treated by radical irradiation M. Loi 1 , B. Detti 2 , G. Simontacchi 2 , V. Di Cataldo 3 , P. Bonomo 2 , L. Masi 3 , R. Doro 3 , I. Bonucci 3 , S. Cipressi 3 , I. Desideri 2 , D. Greto 2 , M. Perna 2 , V. Carfora 2 , G.