ESTRO 2024 - Abstract Book

S2545

Clinical - Urology

ESTRO 2024

2520

Digital Poster

PSA threshold and predictors of metastases on PSMA PET CT for PSA progression post radiation.

Kurian J Puthur 1 , Bhanu Vashistha 1 , Moses Arunsingh 1 , Soumendranath Ray 2 , Jayanta Das 2 , Indranil Mallick 1

1 Tata Medical Center, Radiation Oncology, Kolkata, India. 2 Tata Medical Center, Nuclear Medicine, Kolkata, India

Purpose/Objective:

Prostate Specific Antigen(PSA) threshold for imaging and the modality of imaging at biochemical progression after curative intent radiation therapy is currently not standardized. With the availability of novel imaging modalities like Prostate specific membrane antigen-Positron Emission Tomography(PSMA-PET), it may be possible to detect clinically actionable recurrence early in the natural history of disease progression. We conducted an audit of PSMA PET based evaluation of rising PSA levels after curative intent treatment to audit disease detection, especially metastatic disease, and assess whether assessment prior to the Phoenix criteria yields meaningful results.

Material/Methods:

Sixty-four patients with prostate cancer, treated with radical intent EBRT(External beam radiation therapy) with or without hormonal deprivation therapy and who had a PSMA-PET scan done on raising PSA levels from year 2017 2022 were retrospectively analyzed. Data was taken from Electronic Medical Records and entered in the RedCap database. Descriptive statistics, Chi-square and Mann-Whitney U tests were used for statistical analysis. A logistic regression model was created for the detection of extraprostatic recurrence using the rms package in the R statistical software.

Results:

Fifty-five (85.9%), 6(9.4%) and 3(4.7%) patients were classified into high, intermediate and low risk prostate cancer at diagnosis, respectively. Forty patients (62.5%) had a Gleason score of ≥ 8. Fifty -five patients received 60 Gy in 20 fractions and 9 patients received 35 Gy in 5 fractions. Median Serum PSA at diagnosis was 24.49ng/ml. ADT(Androgen deprivation therapy) was used in 58 (90.6%), of whom 39(67.2%) patients had completed ADT more than a year before the scan at recurrence and 10(17.2%) patients were on ADT at the time of imaging. Median time to recurrence imaging from radiotherapy was 45.3 months (range: 3.5 to 99.9 months ). The median PSA at the time of imaging and the median PSA doubling time were 2.51 ng/ml (range: 0.95 to 44.04) and 4.7 months (range 1.1 to 28.7 months), respectively. Number of patients who had detectable disease on PSMA was 54 (84.6%). PSMA uptake was seen in the prostate in 24 patients (37.5%). Nodal uptake was seen in 25 patients (39.1%), with pelvic nodal uptake in 13 patients and extrapelvic in 21 patients. PSMA uptake was seen in bones in 18 patients (28.1%) and viscera in 11 (17.2%). Any extraprostatic disease was detected in 43 patients (67.2%).