ESTRO 2023 - Abstract Book
S1231
Digital Posters
ESTRO 2023
Median PSA at the time of PSMA PET was 0.7 ng/ml (range 0.17 – 8.3) and median PSA doubling time was 5.4 months (range 1.1 – 42.8). The median time from surgery to PSMA PET confirmed pelvic nodal recurrence was 12.4 months. The median number of positive nodes identified on PSMA PET was 1. Preoperative Roach LNI risk was >15% in 77% of patients and >20% in 63% of patients. There were 54 nodal recurrences identified; 48 (89%) were within standard ENI fields and 6 (11%) were not. Conclusion The Roach formula is used in estimating risk of regional LNI in prostate cancer but there remains ongoing debate as to the ideal cut off level that should be used to identify patients who would benefit most from whole pelvic radiotherapy. PSMA PET is being increasingly used to identify regional and distant metastatic disease and using it to individualize and tailor RT treatment may improve outcomes.
PO-1514 SBRT for clinically localized prostate cancer: a propensity scores analysis between two RT schedules
G. Vullo 1 , E. Moretti 2 , A. Magli 3 , F. Titone 4 , M.A. Signor 4 , C. Foti 2 , M. Guarnieri 2 , M. Valeriani 1 , G. Facondo 1 , M. Trovò 4
1 UOC Radioterapia Oncologica, Sapienza Università di Roma, AOU Sant’Andrea, Radiation Oncology, Rome, Italy; 2 Azienda sanitaria universitaria Friuli centrale, SOC Fisica Sanitaria, Udine, Italy; 3 Azienda Unità locale socio sanitaria Dolomiti, SOC Radioterapia, Belluno, Italy; 4 Azienda sanitaria universitaria Friuli centrale, SOC Radioterapia, Udine, Italy Purpose or Objective To report oncological outcomes and toxicities of a series of clinically localized prostate cancer (PCa) patients treated with SBRT using two RT schedules. Materials and Methods We analysed a prospective database on clinically localized PCa patients treated with SBRT consisting of 42 Gy/7 fx or 36,25 Gy/5 fx on alternate days from January 2013 and September 2020. The inclusion criteria were histologically verified adenocarcinoma, cT1c-T3bN0M0, WHO PS 0-2. No patients received any ADT. SBRT was delivered with volumetric modulated arc therapy (V-MAT). Daily cone beam CT and fiducial markers image-guidance was used. Biochemical recurrence was defined according to Phoenix criteria (nadir +2 ng/mL). Survival analysis was performed using the Kaplan-Meier method and the log rank test was applied to compare the effect of the individual variables (age, ISUP, initial PSA, TNM, NCCN risk classification) on different outcomes. Patients treated with 7 fx and 5fx were matched via propensity score. The following variables were included in the model: age, PSA at diagnosis, ISUP and clinical tumor stage. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicities were graded using the Common Terminology Criteria for Adverse Events,version 5.0. Results Median follow-up was 50 months (IQR, 30,3-69,6). Twenty-five (16%), 48 (30,8%), 43 (27,6%), 31 (19,8%) 8 (5,1%) and 1 (0,7%) patient were classified as very low-risk (VLR), low-risk (LR), favourable-intermediate-risk (FIR), unfavourable intermediate-risk (UIR), high-risk (HR) and very high-risk group according to the NCCN risk classification. After PS matching 130 patients were identified (65 cases treated with 7 fx and 65 with 5 fx). The 5-year OS was 97,4%. Eight (13.5,1%) patients developed biochemical recurrence after a median time of 34 months (range 15–94). Median bPFS was not reached. 5- year bPFS was 97,3%. RT schedule did not influence bPFS before and after PS matching (p 0.34 and p 0.20). Median MFS was not reached. 5- year MFS was 98,6%. RT schedules were not related to LC and MFS before PS (p 0,97 and 0,66) and after (p 0,99 and 0,16). Age, PSA pre-RT, ISUP, T stage and NCCN risk group did not influence OS, CSS, bPFS, LC and MFS before and after PS matching. No acute nor late G ≥ 3 toxicities were reported. Forty-one (26,3%) and 45 (28,8%) patients had G1 and G2 acute GU toxicity. Eleven (7%) and two (1,3%) patients had G1 and G2 acute rectal toxicity. PTV>95cc (p 0,036, OR 2,25, 95% CI 1,05-4,81), PTV Dmedian%> 103,3% (p 0,006, OR 2,71, 95% CI 1,33-5,52), bladder D1ccEQD2>75,5 Gy (p 0,032, OR 1,07, 95% CI 1,10-1,14) were related to G2 GU acute toxicities. Multivariate analysis confirmed PTVcc >95cc (p 0,045, OR 2,25, 95% CI 1,02-4,98) and PTV Dmedian > 103,3% (p 0,02, OR 2,47, 95% CI 1,15-5,23). SBRT schedule was not related to G2 acute GU toxicity (p 0,161). Conclusion SBRT delivered in 5-7 fx represents an effective and safe treatment for clinically localized PCa. No significant difference between 5 and 7 fx was observed.
PO-1515 Intrafractional prostate movements and toxicity in a randomized trial with small-margin radiotherapy
J. Staby Olsén 1
1 Örebro University, Oncology, Örebro, Sweden
Purpose or Objective Moderately hypofractionated radiotherapy (RT) with high dose-rate brachytherapy as boost is considered a suitable treatment option in patients with localized prostate cancer. Hypofractionated RT requires high accuracy in dose delivery to enable reduced treatment margins to minimize the dose to organs at risk. Real-time monitoring of intrafractional prostate movements could theoretically enable higher precision in dose delivery and smaller margins. The present study aimed to investigate whether smaller margins could enable an accelerated delivery of hypofractionated RT (five times vs. three time per week) without increased toxicity. The study also aimed to assess the pattern of intrafractional prostate movements using a high-precision real-time tracking system.
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