Significance of Ga-68-DOTA-TOC-PET/CT in prediction of survival of patients treated with Lu-177-DOTA-TATE

1179 Objectives Ga-68-DOTA-TOC-PET/CT is a well established diagnostic tool in the management of patients with neuroendocrine tumors. In this study we investigated the significance of Ga-68-DOTA-TOC-PET/CT in prediction of the survival of patients treated with Lu-177-DOTA-TATE. Methods 33 patients underwent a Ga-68-DOTA-TOC-PET/CT prior to as well as after completion of PRRT. A tumor to organ-ratio was calculated for every tumor lesion in both scans using SUVmax of selected tumor lesions (liver (LM), lymph node (LN) and bone metastases (BM) as well as the primary (PT)) and of three chosen reference organs (spleen, adrenals and liver). In addition a ΔSUVmax of the respective tumor to organ-ratio was calculated (mean decrease of ΔSUVmax LN/spleen ratio = 0,45; PT/liver ratio = 5,0; LN/adrenals ratio = 1,88 ). The correlation between ΔSUVmax values and overall (OS) and progression-free survival (PFS) was investigated over a median follow-up of 20 months using Kaplan-Meier estimator. The significance level was set a p Results There was a significant correlation between PFS and decrease in the LN/spleen ratio (p=0.048). Additionally a decrease in the LN/adrenals ratio (p=0.061) and PT/liver ratio (p=0.056) was associated with a trend to a longer PFS. No significant correlation with PFS was found for the liver metastases and bone metastases ratios (p>0.1). OS did not correlate with any tumor to organ ratio (p>0.1). Conclusions A decrease in ΔSUVmax in LN/spleen ratio in Ga-68-DOTA-TOC-PET/CT after Lu-177-DOTA-TATE treatment correlates significantly with progression-free survival. Decrease in LN/adrenals and PT/liver ratio also seem to be associated with a longer PFS. There was no correlation between tumor/organ-ratios and OS. Further studies and a longer follow-up are necessary to verify these results