ESTRO 2020 Abstract Book

S623 ESTRO 2020

Clinical data, early and late GI toxicity (RTOG scale) and dose-volume parameters were collected and analyzed. Based on literature, dosimetric parameters such as V15, V30, V40, V45, V50, V60, V70, Dmax, Dmean and median volume of sigma were evaluated. Sigma was contoured 2 centimeters above the PTV with an expansion of 1 centimeter in all directions. Results Fifty-eight patients with prostate acinar adenocarcinoma treated from 2015 to 2018 were analyzed; median age was 72 (range 45-81). Hormonal therapy was administered in 43 patients (74%). Treatment intent was exclusive, adjuvant or salvage in 17 (29.3%), 18 (31%) and 13 (biochemical: 20.7%; macroscopic recurrence: 1.7%) patients, respectively. According to treatment doses (66- 70Gy vs 72-78Gy) and volumes (whole pelvis vs no-whole pelvis), sigma dose-volume parameters were evaluated in 4 subgroups of patients (Table). The median follow-up was of 18.45 months (range 6-39.5). Early and late Grade 1 GI toxicity (diarrhea, tenesmus, rectal bleeding) was reported in 12% and 5.2% patients, respectively; early and late Grade 2 GI toxicity (diarrhea, tenesmus, rectal bleeding, fecal incontinence) was reported in 10.3% and 1.7% patients, respectively and no early and/or late GI toxicity > Grade 2 was reported. Overall, limited volumes of sigma in treatment field was reported in all subgroups with no significant differences between the 4 subgroups. Furthermore, high doses were delivered to limited volumes of sigma with no early and late GI toxicity > G2. Conclusion Our results on a limited number of patients did not show Grade > 2 GI toxicity and high doses (V50%, V60%, V70%) were delivered only to small volumes of sigma, although specific constraints for sigma were not applied during planning optimization. These preliminary data seem to be promising and applicable to daily clinical practice, pointing out the ability of IMRT/VMAT to reduce acute and late toxicity. The study is still ongoing on a larger number of patients and a longer follow-up. PO-1184 The significance of nomograms for predicting node metastasis in 68ga-PSMA-PET/CT in prostate cancer C. Onal 1 , O.C. Guler 1 , N. Torun 2 , M. Reyhan 2 1 Baskent University Adana Dr Turgut Noyan Research and Treatment Center, Department of Radiation Oncology, Adana, Turkey ; 2 Baskent University Adana Dr Turgut Noyan Research and Treatment Center, Department of Nuclear Medicine, Adana, Turkey Purpose or Objective To evaluate the accuracy of clinical parameters and nomograms in predicting 68 Ga-PSMA positive lymph node metastasis as initial staging examination for prostate cancer patients. Material and Methods The clinical parameters of 271 treatment-näive prostate cancer patients were retrospectively analyzed. All patients had 68 Ga-PSMA-PET/CT for initial staging procedure. The correlation between serum PSA, SUV max of primary tumor and lymph node metastasis was evaluated. The risk of lymph node involvement was calculated using Roach formula (RF), Yale formula (YF) and Partin nomogram (PN) and compared with 68 Ga-PSMA-PET/CT

findings with ROC analysis. Patients with distant metastasis and receiving hormonotherapy before 68 Ga- PSMA-PET/CT delivery were excluded. Results Median age was 68 years (45 – 75 years). Median pre- treatment PSA and SUV max of primary tumor were 17.6 ng/dL (2.3 – 301.0 ng/dL) and 12.8 (4.3 – 84.3), respectively. 234 patients (86%) were treated with definitive radiotherapy, and 37 patients (14%) were treated with radical prostatectomy. The clinical T stages were: 12 patients (4%) T2a, 97 patients (36%) T2b, 51 patients (19%) T2c, 39 patients (14%) T3a, and 72 patients (27%) T3b. 81 patients (30%) had regional lymph node metastasis. 139 patients (51%) had GS 7, 61 patients (23%) had GS 8, 61 patients (23%) had GS 9 and 10 patients (3%) had GS 10 disease. The area under curve (AUC) for PSA and SUV max of primary tumor regarding lymph node metastasis were 0.690 (95% CI 0.620 – 0.761) and 0.650 (95% CI 0.575 – 0.725), respectively. The cut-off values of PSA and SUV max for predicting lymph node metastasis were 21.2 ng/dL and 13.9, respectively. The AUC’s for RF, YF and PN for detecting 68 Ga-PSMA positive lymph node metastasis were 0.745 (95% CI 0.685 – 0.805), 0.731 (95% CI 0.668 – 0.794), and 0.704 (95% CI 0.642 – 0.766), respectively (Figure 1).

Conclusion The clinical parameters may help to predict the risk of lymph node metastasis in prostate cancer patients. However RF is still a reliable tool to predict lymph node metastasis in prostate cancer patients. Because the conclusion of the present study is premature and 68 Ga- PSMA-PET/CT is not accepted as a routine imaging modality for PC staging, the long-term results of this study are required to interpret these findings in clinical practice. PO-1185 Results of prostate cancer patients treated by integrated boost to dominant intraprostatic lesion A.R. Alitto 1 , M. Buwenge 2 , G. Macchia 3 , M. Ntreta 2 , G. Siepe 2 , E. Galofaro 2 , F. Bertini 2 , M. Ferioli 2 , E. Mazzeo 4 , E. Ippolito 5 , G. Mantini 6 , M. Ferro 3 , A. Re 3 , S. Cilla 7 , V. Valentini 6 , F. Deodato 3 , A.G. Morganti 2 , S. Cammelli 2 1 Fondazione Policlinico Universitario A. Gemelli - IRCCS, Dipartimento di Scienze Radiologiche- Radioterapiche ed Ematologiche-UOC di Radioterapia Oncologica- Gemelli- ART, Rome, Italy ; 2 Azienda Ospedaliera-Universitaria S.Orsola-Malpighi, Dipartimento di Medicina Specialistica Diagnostica e Sperimentale-DIMES- U.O. di Radioterapia, Bologna, Italy ; 3 Fondazione "Giovanni Paolo II"- Università Cattolica del Sacro Cuore, UO di Radioterapia, Campobasso, Italy ; 4 Az. Ospedaliero Universitaria of Modena-Policlinico, U.O. di Radioterapia, Modena, Italy ; 5 Campus Bio-Medico Universitario, U.O. di Radioterapia, Roma, Italy ; 6 Fondazione Policlinico Universitario A.