Abstract Book

S858

ESTRO 37

1 University Hospitals HM Sanchinarro&HM Puerta del Sur, Radiation Oncology, Madrid, Spain

internal Medicine and Metabolic and Endocrine Disease-, Perugia, Italy

Purpose or Objective According to an estimated 1.5 Gy alpha/beta ratio prostate cancer may be more sensitive to hypofractionated radiotherapy (Hypo-RT) than conventional schedule.Several phase III clinical trials exploring hypofractionation in localized prostate cancer showed no significant differences in clinical outcomes, efficacy and tolerance to conventional RT , while randomized data in support of hypofractionated radiotherapy after radical prostatectomy are lacking. Most trials administered the IPSS questionnaire to evaluate GU toxicity. We designed a prospective observational study to investigate Hypo-RT in adjuvant and salvage prostate cancer patients with the aim of evaluate acute and late genitourinary (GU) toxicity with uroflowmetry. Material and Methods Between March 2013 and October 2016, 112 patients were enrolled in the study. All had undergone Radical Prostatectomy. Hypofractionated adjuvant-RT ( 2.25 Gy daily for 29 fractions; a total 65.25 Gy) was administered to 40 patients with high risk features . Hypofractionated salvage-RT (2.25 Gy daily for 32 or 33 fractions; total 72 -74.5 Gy) was prescribed for 72 patients with biochemical/local recurrence.Most patients had uroflowmetry before starting RT. Uroflowmetry was repeated at different time-points of the follow-up and the result at the latest follow-up was used in the statistical analysis. Results No patient in either group was affected by GU-grade 3 toxicity at a median follow up of 18 months . 37 (92,5%) and 65 (90%) patients submitted to adjuvant and salvage treatment had baseline Uroflowmetry before starting radiotherapy. At baseline, maximum flow, median flow and post- voided residual were abnormal in 12 patients (32.5%) and in 17 (26%) of adjuvant-RT and salvage-RT group, respectively. Adjuvant-RT: 24/37patients (65%) repeated uroflowmetry after treatment and 6/24 (25%) patients had abnormal values. Salvage-RT: 57/67 (85%) patients repeated uroflowmetry after treatment and 18/57 (31.5%) had abnormal values. Although RT did not impact significantly on uroflowmetry, the chi square test showed the median maximum flow was significantly reduced after salvage-RT (24ml/sc vs 26.7ml/sc; p=0.013).Whether administered in Adjuvant or Salvage RT, hypofractionation schedules appeared safe as RT did not impact significantly on maximum or median flow or post-voided residual. Not unexpectedly, however, when compared with patients who were administered adjuvant RT, maximum flow was reduced in patients who received salvage RT, probably because of the higher dose. Conclusion Hypofractionated radiotherapy in adjuvant and salvage setting was safe; no patient developed GU toxicity > grade 2.Uroflowmetry was a non-invasive, low expensive test that evaluates urinary function and it could minimize subjective bias when used before and after RT. EP-1595 Comparative analysis of PSA kinetics related to 4 different radiotherapy modalities A. Acosta Rojas 1 , A. Montero 1 , J. Valero 1 , B. Alvarez 1 , O. Hernando 1 , E. Sanchez 1 , M. Lopez 1 , M. Garcia-Aranda 1 , R. Ciervide 1 , R. Alonso 1 , X. Chen 1 , C. Rubio 1

Purpose or Objective To evaluate differences in time to reach nadir PSA (nPSA) in low and intermediate-low-risk prostate cancer patients undergoing 4 different radiotherapy approaches: external beam IMRT vs. stereotactic body radiotherapy (SBRT) vs. high dose rate brachytherapy (HDR) vs low dose rate From January-2012 to August-2017, 117 patients with a median age of 65 y/o (range 49-84 y/o) and with low (89p, 76%) or intermediate-low (28p, 24%) risk prostate cancer patients according to NCCN criteria were admitted at our institution. Clinical stage was T1a-cN0M0 in 100 patients (85.5%) and T2a-bN0M0 in 17 patients (14.5%). Gleason 4-6 in 98 p (84%); Gleason score 7 (3+4) in 19 p (16%). Patients were treated with 4 different techniques: - 21 p (18%) underwent HDR (19 Gy/in 1 fraction). - 43 p (37%) underwent permanent LDR implant with I-125 seeds (144-160 Gy). - 33 p (28%) were treated by external-beam IMRT: 6 p received a total dose of 70 Gy in 28 fractions whereas remaining 27 p were treated up to a total dose of 63 Gy in 21 fractions. - 20 patients (17%) were underwent SBRT up to a total dose of 36.25 Gy in 5 fractions. Patients were followed at 3-months intervals with seriated PSA determinations. We calculated value of PSA- nadir (PSAn) and time to reach PSA. Additional calculations regarding different radiation alternatives included PSA halving-time and velocity of PSA decrease. Results With a median follow-up for the entire cohort of 26 months (range 2-105 months) all patients are alive; biochemical relapse was observed in 13 patients (11%), of which 9 had been treated with LDR (median 34 months (17-69)) and 4 patients with IMRT. All relapses after IMRT corresponded to patients treated up to 70 Gy in 28 fractions. Median follow-up varies between different options: IMRT 27 months (range 8-101); SBRT 14.5 months (2-44); LDR 38 months (7-15); HDR 13 months (4-29). Median PSAn for the entire cohort was 0.8 ng/ml (0.01- 7.08) with median time to PSAn of 14 months (1-99). Median value for PSAn was significantly higher in those patients undergoing HDR (p 0,001). Velocity of PSA reduction was faster in patients treated by HDR and SBRT and being significantly slower in LDR patients (p 0,003). PSA halving-time was shorter with HDR, IMRT and SBRT compared to LDR (p 0,046) (Table 1). brachytherapy (LDR). Material and Methods

Conclusion Despite the differences in length of follow-up among the different therapeutic options, HDR and external SBRT appear to be the fastest-decreasing PSA levels, with a shorter halving time of initial PSA. Both longer follow-up