ESTRO 2023 - Abstract Book

S336

Sunday 14 May 2023

ESTRO 2023

Overall, 1029 patients (training set n=798, internal and external validation set n=271 and 50) with a median follow-up of 33 months were included. On PSMA-PET, 427 (42%) and 313 (30%) patients had local and nodal recurrences, respectively. Elective pelvic lymphatics were irradiated in 368 (36%) patients. All patients received sRT to the prostatic fossa receiving a dose of <66 Gy, 66-70 Gy and >70 Gy in 103 (10%), 551 (54%) and 375 (36%) patients, respectively. Androgen deprivation therapy (ADT) was given in 325 (32%) patients. On multivariable Cox regression analysis, pre-SRT PSA, ISUP grade, pT stage, surgical margins, ADT use, sRT dose and nodal recurrence on PSMA PET were significantly associated with FFBF. The nomogram concordance index was 0.72 and 0.67 for FFBF in internal and external validation, respectively. Conclusion We present a validated contemporary nomogram which can estimate individual patient outcomes after PSMA-PET guided sRT. Positive lymph nodes on PSMA-PET seem to be a new risk factor for BR after sRT.

OC-0436 A Delphi consensus study on SBRT for oligometastatic renal cell carcinoma (RCC) an ESTRO ACROP study G. Marvaso 1,2 , M. Zaffaroni 3 , S. Siva 4 , D. Pasquier 5 , M.G. Vincini 1 , G. Corrao 1 , B.A. Jereczek-Fossa 3,6 , O.B.O.T. ESTRO ACROP group 7 1 IEO, European Institute of Oncology IRCCS, Division of Radiation Oncology, Milan, Italy; 2 University of Milan, Department of Oncology and Hemato-Oncology, Milan, Italy; 3 IEO, European Institute of Oncology IRCCS, Division of Radiation Oncology , Milan, Italy; 4 Peter MacCallum Cancer Centre, University of Melbourne, Sir Peter MacCallum Department of Oncology, Melbourbe, Australia; 5 Centre Oscar-Lambret, Service de radiothérapie oncologie, Lille, France; 6 University of Milan, Department of Oncology and Hemato-Oncology , Milan, Italy; 7 ESTRO ACROP, ESTRO ACROP, Milan, Italy Purpose or Objective Currently, there are no guidelines on the management of oligometastatic RCC with SBRT. The purpose of this ESTRO ACROP project is to explore the expert opinion on the management of oligometastatic RCC patients using SBRT on extracranial metastases, with the aim of developing consensus recommendations to help with management decisions for treatment, improve patient selection, prescription doses and management alongside systemic therapy. Materials and Methods A questionnaire on SBRT in oligometastatic RCC was prepared by a core group and reviewed by a panel of 10 prominent experts in the field. The final version of the questionnaire included 58 questions dealing with controversial issues related to oligometastatic RCC and SBRT. It was implemented online via Google Forms and sent to clinicians identified as key opinion leaders. The Delphi consensus methodology was applied and involved sending three rounds of questionnaires to the experts. After the conclusion of each round, a fully anonymised summary of their and others’ responses was provided to the participants, in order to drive the panellists towards the consensus. The agreement threshold was set at 80%. Results Among the 43 contacted professionals, a total of 25 experts (58%) agreed to participate. Responders, characteristics are reported in Table 1. Two out of the three planned rounds of responses have been completed. At the end of the first round, participants were able to find consensus on 7 out of 52 clinical questions. Specifically, SBRT was indicated as the elective treatment choice for RCC bone metastases (80%) and for adrenal lesions (88%) independently from site. Small bowel, duodenum, and stomach were the major dose limiting organs for both pancreatic and adrenal lesions, with the addition of kidney for the latter. At the end of the second round, one further question reached the consensus, with 83% of responders agreeing on an upper threshold of 3 lesions for SBRT in the oligoprogressive setting. A summary of the main areas of agreement and disagreement is reported in Table 2.

Table 1. General information about the writing committee population