ESTRO 2024 - Abstract Book

S2439

Clinical - Urology

ESTRO 2024

To analyze the possible changes in treatment that could occur in those cases that present positive results of the study.

Material/Methods:

116 patients were retrospectively selected from participating centers with biochemical relapse of prostate cancer after primary treatment. All patients had a conventional negative study (CT-scan, GGO, pelvic MRI) or negative PET Choline, all 116 patients underwent the study with 18F-PSMA DCFPyL PET/CT. All patients had PSA values less than 2 ng/ml before the study. Analysis of the studies was performed by two physicians with expertise in nuclear medicine and classified dichotomously as positive or negative/inconclusive based on the findings. The diagnostic ability of the study was determined according to PSA values as well as cluster density. Descriptive statistical analysis was performed. RoC curves (sensitivity vs. 1-specificity) and the corresponding areas under the curve were calculated to assess the predictive power of the study. The overall detection rate was analyzed as a function of the number of lesions the study was able to diagnose compared to the conventional study and classified according to percentage of local relapse, adenopathy, bone or visceral lesions.

Results:

Retrospective analysis showed that 56.9% of patients (66/116) had positive PET-PSMA results. The median pre-study PSA was 0.60ng/ml and a directly proportional correlation was observed between PSA values and PET-PSMA diagnostic ability with statistically significant differences in the positive group (AUC 0.77). The optimal cut-off point calculated according to RoC curves (sensitivity vs. 1-specificity) was 0.55 ng/ml to obtain a sensitivity of 75% (AUC 0.74).

In the study of densities by group, there was a marked clustering of patients with positive PSA values between 0.5 - 1.0 ng/ml and inconclusive results when PSA was less than 0.5ng/ml.

From the sum of all positive PET-PSMA studies, a total of 127 lesions were found in the 116 patients who were negative in conventional studies (CT-scan, GGO, pelvic MRI) and/or PET-Choline (19% prostate/bed, 56% adenopathies, 22% bone lesions and 3% visceral metastases).

In the total number of patients selected for the study, once they underwent PET-PSMA, there were changes in the therapeutic management of all patients with positive results, representing 56.9% of the sample.

Conclusion:

PET-PSMA was shown to be an excellent tool showing a higher diagnostic capability than other diagnostic tests in patients with biochemical relapse of prostate cancer. The greatest diagnostic benefit in our study was obtained in those patients who were grouped with PSA values between 0.5 - 1-0 ng/ml. All patients with positive results in the study underwent changes in therapeutic management.

We truly believe that we are in the era of PET-PSMA and based on future data analysis we will probably find greater benefit with lower PSA values.