ESTRO 36 Abstract Book

S720 ESTRO 36 _______________________________________________________________________________________________

PSA dosage every 3 months after SBRT: considering the pre-SBRT PSA as reference, a decrease in PSA of more than 10% identified responder patient, whereas an increase of more than 10% identified a biochemical progression. The other cases were classified as PSA stabilization. In case of PSA increase during the follow-up, imaging was performed to evaluate clinical progression. Toxicities were assessed with clinical examination every 6-9 months: acute toxicities were reported in the first 6 months after SBRT. Results A hundred twenty-seven lesions were treated in 95 patients with a median dose of 24 Gy given in 3 fractions. Median pre-SBRT PSA was 3.5 ng/mL. Seventy patients were treated for a single lesion, 25 for 2-4 lesions. In 9 patients SBRT was performed as a re-irradiation. In 35 patients androgen deprivation therapy (ADT) was added to SBRT. Median follow-up was 18.5 months . One patient was not valuable due to short follow-up. Biochemical response, stabilization and progression were observed in 64 (68.1%), 10 (10.6%) and 20 (21.3%) out of 94 patients. In the 57 patients treated with salvage SBRT alone (with no concomitant therapy), biochemical response, stabilization and progression were observed in 38 (66.7%), 9 (15.8%) and 10 (17.5%) cases, respectively. In 17 patients (29.8%) with progressive disease after SBRT, ADT started in a median time of 7.2 months (range 2.4–32.1). Clinical progression was observed in 31 patients (33.0%) after 15 months (median time). In-field progression occurred in 12 lesions (9.4%). 2-year local control and PFS rates were 84% and 30%, respectively (fig. 1-2). Age>75years correlated with better biochemical response rate. Age>75years, concomitant ADT administered up to 12 months and pelvic LN involvement correlated with longer PFS. Acute toxicity included urinary (6 and 1 G1 and G2 events, respectively) and rectal events (1 G1 event). Late toxicity included urinary (2 G1 and 3 G2 events). All toxicities were reported in patients treated for pelvic LN. No toxicity were reported in patients with extra-pelvic LN. At the time of the analysis, 32 (34.0%) patients are alive with no evidence of disease, 60 (63.8%) are alive with clinically evident disease, 2 patients (2.1%) died.

Conclusion SBRT is safe and offers excellent in-field control. At 2 years after SBRT, 1 out of 3 patients is progression-free. Further investigation is warranted to identify patients who may benefit most from SBRT and to define the optimal combination with ADT EP-1343 Is stereotactic body radiation therapy a viable option for elderly patients with prostate cancer? C. Franzese 1 , G. D'agostino 1 , L. Di Brina 1 , L. Cozzi 1 , T. Comito 1 , D. Franceschini 1 , F. De Rose 1 , P. Navarria 1 , E. Clerici 1 , A. Ascolese 1 , A. Tozzi 1 , C. Iftode 1 , S. Tomatis 1 , M. Scorsetti 1 1 Istituto Clinico Humanitas, Radiotherapy and Radiosurgery, Rozzano Milan, Italy Purpose or Objective Data regarding the treatment of elderly patients with prostate cancer show that Radiotherapy (RT) is associated with a cancer specific mortality risk reduction of 2.6% at 10 years, even after adjusting for several confounders including 12 comorbid conditions. The aim of the present study is to evaluate the efficacy and toxicity of Stereotactic body radiation therapy (SBRT) in a group of elderly patients affected by low and intermediate risk prostate cancer. Material and Methods Patients aged ≥ 75 years, with biopsy-confirmed prostate cancer were enrolled. Inclusion criteria were: initial prostate-specific antigen (PSA) ≤ 20 ng/ml, Gleason Score ≤ 7, International Prostate Symptom Score ≤ 7. Gantry-