Untersuchung zum Diagnostischen Impact einer Dual-time-PET/CT mit PSMA-Liganden beim Prostatakarzinom sowie mit DOTATOC bei neuroendokrinen Tumoren

The present study is a retrospective analysis of data, focusing on the diagnostic impact of dual phase PET/CT-examinations, using Gallium 68-DOTATOC in neuroendocrine tumors and Gallium 68-PSMA in prostate cancer. The aim was to show whether there is a diagnostic benefit of the biphasic approach or not. In total, 194 data sets of dual-time PET/CTs were re-examined under supervision of an experienced specialist in nuclear medicine. The findings of the first scan were then compared to synoptic findings of both the first and the second pictures. By calculating the Cohens kappa coefficient, the chance adjusted agreement of the two findings was quantified. The main focus was on comparing sensitivity and specificity of the mono- and biphasic PET/CT. If available, the histological findings were used as gold standard. If not available, we applied a reference standard based on clinical and radiological findings of the following two to five years as far as possible. The direct comparison of each patient´s pair of findings showed relevant differences: By the second scan, there was a change of findings in nearly half of all DOTATOC cases and in about a third of all scans with PSMA. Furthermore, a change of the TNM status could be seen in 45,5% of the changes within the neuroendocrine tumor group and 66,7% within the prostate cancer group. Among the DOTATOC cases, there was a strong accumulation of change of findings in both pancreatic and gastrointestinal lesions. This accumulation compared to the average change in DOTATOC-positive lesions was statistically significant. The calculation of Cohens kappa showed a merely moderate agreement in the findings of both groups, which can also be interpreted as an indication of a quite big difference between the pairs of findings. By the dual-timed scan with PSMA, there was an obvious increase of both sensitivity and specificity from 81,8% to 95,7% and from 66,7% to 100% (95%-CI: sensitivity from 61,5–92,7% to 79,0–99,2%; specificity from 39,1–86,2% to 74,1-100%). In lack of enough cases with either histological or clinical and radiological reference standard, there could not be shown a statistical significance for this improvement. But indeed, it was found evidence for a significant increase of both sensitivity from 53,3% to 93,3% (95%CI: 39,0 - 67,1% to 82,1 - 97,7%) and specificity from 54,6% to 86,4% (95%-CI: 34,7 - 73,1% to 66,7 - 95,3%) by the biphasic PET/CT with DOTATOC.