ESTRO 2023 - Abstract Book

S317

Sunday 14 May 2023

ESTRO 2023

Conclusion The steerable needle approach allows for more flexibility in needle placement, mitigation of deflections by countersteering and the avoidance of PAI. The curved trajectories can be easily planned in the OCP TPS and implantation can be performed with excellent agreement between pre-treatment plan and postimplant treatment plan. An adequate dose distribution can be achieved without prostate downsizing, and hence, men with enlarged and/or excessive PAI can be considered to be treated with HDR BT. PD-0416 Alternative reirradiation salvage-radiotherapy for recurrent prostate cancer after ldr-brachytherapy O. Muñoz Muñoz 1 , E. Gomis Sellés 1 , B.D. Delgado León 1 , J.L. López Guerra 1 , P. Cabrera Roldan 1 1 Virgen del Rocio University Hospital, Oncology Radiotherapy, Sevilla, Spain Purpose or Objective This retrospective study evaluated at the tolerability and outcomes of Reirradiation Salvage external beam radiotherapy (ReS-EBRT) for locally recurrent prostate cancer (LRPC) after definitive prostate brachytherapy (BQ) Materials and Methods Between October 2012 and June 2022, 21 patients with locally recurrent prostate cancer after brachytherapy (BQ) with biopsy-proven local-only recurrence and uroflowmetry test measure QMax > 12 ml/s and IPSS < 12, were planned to receive ReS-EBRT: 60Gy +/- 55,2Gy (24 fractions at 5/weeks) to the prostate and seminal vesicles respectively; VMAT/IMRT technology with daily IGRT, previously urinary catheterization throughout the all treatment; The target volume consisted of the CTVp: prostate and CTVv: seminal vesicles; PTVp: CTVp + 3-5mm and PTVv: CTVv + 3-5mm and finally, the organs at risk (OARs) were delimited Bladder, urethra, rectum, femoral-heads, penis bulb. We evaluated biochemical failure (BF) was definited as PSA < post-treatment nadir+2, overall survival (OS), and acute/late gastrointestinal-urinary toxicities (CTCAE v 4.03) weekly during radiotherapy treatment and monthly after completion of treatment. Results The median age of 68 years (range 59-79). 45% (9/20) were low risk, 30% (6/20) intermediate risk, 10% (2/20) high risk and 15% (3/20) not specified. Median follow-up was 24 months (range 1-101,9m). Patients were treated in IMRT Vs VMAT (15/5). All patients received 60 Gy (2.5 Gy/fraction) to the prostate and 30% (6/20) 55.2Gy (2,3 Gy/fraction) to the seminal vesicles. Furthermore, 40% (8/20) received androgen deprivation therapy (ADT) concurrent for a median 6 months, starting 2 months prior RT. All patients completed EBRT. No patient has presented BF since the end of treatment with a median PSA nadir 0,14ng/mL (0,01-0,40), in an unspecified nadir PSA patient due to short follow-up period. All patients are alive at the present time. And acute/late gastrointestinal-urinary toxicities (CTCAE v 4.03): 25% (5/20) patients had acute urinary toxicities Grade > 3. In addition, Rectitis Grade > 2 were observed in 10% (2/20); No acute grade 4/5 toxicities were noted. Chronic toxicity, no grade Grade > 3 toxicities were noted. Conclusion Our data suggest that the treatment of locally recurrent prostate cancer with Reirradiation Salvage External Beam Radiotherapy could provide adequate disease control and result in a safe technique that provides the patient with an alternative in the natural history of their disease. PD-0417 Multisector dosimetric analysis to determine in-vivo dosimeter positions in prostate brachytherapy. O. Houlihan 1,2 , S. Esteve 3 , O. McLaughlin 2,3 , G. Workman 3 , M. Byrne 3 , K. Prise 2 , A. Hounsell 3 , D. Mitchell 1 , S. Jain 1,2 1 Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Clinical Oncology, Belfast, United Kingdom; 2 Queen’s University Belfast, Patrick G. Johnston Centre for Cancer Research, Belfast, United Kingdom; 3 Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Radiotherapy Medical Physics, Belfast, United Kingdom Purpose or Objective To determine the optimal positions within the prostate for in vivo dosimeters, developed as part of the EU H2020 Origin project, using multisector dosimetric analysis to optimise brachytherapy delivery.

Materials and Methods