ESTRO 2023 - Abstract Book

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ESTRO 2023

Treatment using scheme: 10 Gy inverse brachytherapy boost with implantation of gold markers and subsequent prostate or pelvic EBRT with ADT is effective and well tolerated and feasible. Implantation of gold markers during BT session can reduce workload of radiotherapy department.

PO-2198 MRI guided nodular salvage Brachytherapy after Prostatectomy and EBRT. 3 years outcome

P. Willisch Santamaria 1 , B. Andrade Alvarez 2 , E. Cespon Outeda 3 , L. Rojas Bua 4 , M.L. Vazquez de la Torre Gonzalez 1 , A. Lopez Medina 5 , S. Montemuiño Muñiz 1 , M. Martínez Agra 6 , E. Castelao 7 , V.M. Muñoz Garzon 1 1 Galaria, Radiation Oncology, Vigo, Spain; 2 Galaria, Radiophysis , Vigo, Spain; 3 Sergas, Urology, Vigo, Spain; 4 Fundación biomédica Galicia Sur, Radiation Oncology, Vigo, Spain; 5 Galaria, radiophysics, Vigo, Spain; 6 Povisa, Radiation Oncology, Vigo, Spain; 7 Fundación biomedica galicia sur, Fundación biomedica galicia sur, Vigo, Spain Purpose or Objective Patients who relapse locally after radical prostatectomy and external radiation therapy, treated with local brachytherapy are presented to delay treatment with hormonal blockade and new therapeutic target. Materials and Methods From April 2016 to December 2020, 16 patients have been treated with an average age of 67,64 years (52-77). Inclusion criteria is: Progressive increase of PSA after Prostatectomy and EBRT, local recurrence positive in perfusion- diffusion MRI and Coline PET in prostatectomy bed, treatment with RP and EBRT almost one year before and IPSS <15.

The prescribed dose and fractionation was (17-25,5 Gy) in 2-3 fractions.

Prior to the procedure, a volumetric T2-weighted MR with slice thickness and spacing of 3mm is done.

The MR to US image registration is manually done using the TPS translation and rotation tools at the moment of the procedure so the fused image set is used for contouring the target, with a median volume: 2,43cc (0,32-11,27).

In order to reduce the dose to rectum, High density Hyaluronic Acid is injected between rectum and target volume.

A preplanning before insertion is done. After insertion, needles (Average: 5(3-13) are reconstructed, live plan is re- optimized and treatment is delivered. Results With a medium follow-up of 37,7 months, 43,75% (7 patients) have been able to delay treatment with hormone blockade for 2 years, and 18,75% (3 patients) up to 3 years. In the subanalysis of this data we have obtained a complete response maintained in 18.75%. Of the 25% (4 patients) who relapsed after 2 years, 3 were done locally, 2 at the treatment site and 1 remotely. The longest response time has been observed in patients with a single poor prognostic factor (T3b and/or R1) and with BED greater than 220 Gy.

Treatment toxicity was acceptable with a grade 3 percentage of 18.75%.

Conclusion Patients with good prognostic factors and who receive a BED dose greater than 220 Gy are good candidates for Re-salvage for nodular locally recurrent prostate cancer by focal HDR-BT guided by MRI-US

Further studies are needed.

PO-2199 Nadir PSA in prostate brachytherapy: relationship with biochemical control and clinical results.

S. Rodriguez Villalba 1 , D. Guevara Barrera 1 , J. Pérez-Calatayud 1,2 , F. Blazquez Molina 1 , M. Santos Ortega 1

1 Hospital Clinica Benidorm, Radiation Oncology Department, Benidorm, Spain; 2 La Fe University and Polytechnic Hospital, Radiation Oncology Department, Valencia, Spain Purpose or Objective To evaluate nadir prostate-specific antigen (nPSA) and its relationship with biochemical failure (BF), local failure (LF), lymph node failure (LNF) and distant metastases (DM) in prostate cancer (PC) patients, treated with LDR and HDR brachytherapy (BT). Materials and Methods We retrospectively analyzed 140 patients diagnosed PC treated between 2005-2019 with exclusive BT. Sixty four patients treated with LDR (160 Gy) and 76 with HDR (2 implants of 13.5 Gy each). nPSA was grouped into 4 categories: PSA 0.2 ng/mL (group 1), >0.2 to 0.5 ng/mL (group 2), >0.5 to 1.0 ng/mL (group 3) and >1.0 ng/m (group 4). BF was determined using the Phoenix definition (nadir +2). All of the treatments have been done by the same Radiation Oncologist. In addition, the Physicist team followed a strict protocol to assure uniformity. It guarantees BT contouring plus and the technical process, maintain a high degree of homogeneity.