Ziel/Aim Patients with metastatic castration resistant prostate cancer routinely undergo PSMA-PET
to evaluate the efficacy of PSMA targeting radioligand therapy (Lu-PSMA). Despite
the presence of PSMA expressing metastases, PSMA-negative but FDG-positive metastases
are associated with worse response to Lu-PSMA therapy and shorter overall survival.
Current assessment is based on visual criteria with reduced reproducibility. Reproducible
analysis of PSMA or FDG positive tumor volume is needed for an optimized patient selection.
To this end, we used a semi-automated approach to quantify the metabolic tumor volume
and mismatch in PSMA- and FDG-PET aquisitions prior to Lu-PSMA therapy.
Methodik/Methods Patients who were included in this retrospective analysis received both PSMA- and
FDG-PET CTs to evaluate eligibility for Lu-PSMA therapy. The metabolic tumor volume
was quantified both in the PSMA and FDG PET scan using the semi-automatic software
MICIIS (Siemens), that assists in the exclusion of physiological uptake by neural
networks. All metastases were segmented and labelled with the anatomical location.
Ergebnisse/Results A total of 44 patients were included in this analysis. 14 (32%) of these patients
had a relevant PSMA- FDG+ mismatch which led to an exclusion from a Lu-PSMA therapy,
whereas 30 (68%) patients showed no mismatch and received Lu-PSMA therapy as planned.
Overall survival was significantly longer for patients without PSMA- FDG+ mismatch
versus mismatch (median 15,1 (CI95: 7,5-22,7) vs. 6,8 (Ci95: 2,0-11,6) months; p = 0,027).
Schlussfolgerungen/Conclusions The semi-automated delineation of PSMA positive or FDG positive metastases is feasible
and easy-to-use for PSMA-negative/FDG-positive mismatch quantification. Organ-wise
quantification of PSMA and FDG tumor volume offers the potential for more detailed
patient stratification. Further studies and analyses are needed to determine association
with oncologic outcome.
