ESTRO 2023 - Abstract Book

S1190

Digital Posters

ESTRO 2023

Materials and Methods Patients included in the present analysis had undergone radical prostatectomy (with/without extended pelvic lymph node dissection), and presented with BCR in accordance with the European Association of Urology. The imaging protocol consisted of MRI (chin to thighs), 18F/68Ga-PSMA PET/CT (vertex to thighs) and PET/mpMRI of the pelvic region, performed sequentially. The PET/CT, PET/mpMRI and mpMRI were evaluated separately by specialists in nuclear medicine and radiology and then in consensus. Imaging recurrence was defined as local/loco-regional/metastatic disease according to consensus. This was compared to corresponding readings of mpMRI only. Change of treatment due to PSMA-PET was defined by change from intended treatment for cases where a) imaging recurrence according to consensus differed from mpMRI and b) this difference resulted in upgrading of disease necessitating other treatment than observation or standard salvage RT of the prostatebed +/-/ elective RT of the pelvic region. Differences between groups were assessed by the Wilcoxon rank-sum test (p<0.05 considered statistically significant). Results From May 2020 to March 2022, 100 patients were included and eligible for analysis (see table for clinical data). The median PSA level at time of imaging was 0.38 ng/ml (interquartile range (IQR) 0.21-0.61). Recurrent disease was detected in 42% of patients based on PET/CT/mpMRI, 42% presented with recurrent disease, 8 % were uncertain and 50% had no detected recurrence. Recurrent disease was detected in 17% based on MRI/mpMRI only, 9% were uncertain and 74% had no recurrence. For 20 patients (20%), PET/CT/mpMRI uncovered more advanced disease leading to change of treatment. 6 had metastatic disease incompatible with curative treatment and initiated hormone therapy only. 10 patients had recurrence in loco regional lymph nodes and were referred to standard treatment consisting of hormone therapy and RT of the pelvic region, but including dose escalation to affected lymph nodes. 4 patients had single metastatic skeletal lesions compatible with stereotactic RT or dose escalation within the elective RT volume. Median PSA level of patients with detected recurrence (PET/CT/mpMRI) was 0.41 ng/ml (IQR 0.31-1.0), significantly higher than the group with no detected recurrence (0.30 ng/ml, IQR 0.23-0.47). Conclusion In this low-level PSA patient group, PSMA-PET/CT/MRI identified recurrent disease in 42 %, more than twice as many patients as mpMRI. 20 % of the patients presented with advanced disease demanding change of treatment based on PSMA PET.

PO-1469 dose escalation in hypofractionated radiotherapy in prostate cancer : early and late toxicity

K. Quintin 1 , G. Crehange 2 , P. Graff 3 , S. Krhili 3

1 Institut Curie, Radiotherapy, Paris, France; 2 institut Curie , Radiotherapy, Paris , France; 3 Institut Curie , Radiotherapy , Paris , France Purpose or Objective The prostate adenocarcinoma is the most frequent cancer in men with an annual incidence of 50 400 new cases in France. One of the greatest therapeutic options for the early staged cancers is external radiotherapy. Although hypofractionated radiotherapy has proven a similar efficacity to external radiotherapy, it still isn’t a standard in France. The main purpose of this study is to evaluate the tolerance during and after treatment (4-6 months and 5 years post exposition) among patients that were treated with mild hypofractionated radiotherapy with dose escalation for a prostatic adenocarcinoma. We will also report the data on progression-free survival, specific survival and global survival. Materials and Methods 212 patients were treated consecutively between February 2016 and March 2018. The dose of 75 Gy was delivered in 30 fractions to the prostate and the proximal seminal vesicles (eqd2 = 82.5 to 85.7 Gy delivered in fractions of 2 Gy for an α / β of 1.5 à 3). A hundred and ninety-five patients (92 %) also received a pelvic lymphatic irradiation (46 Gy delivered in 23