The role of baseline Ga-68 DOTATATE positron emission tomography/computed tomography in the prediction of response to fixed-dose peptide receptor radionuclide therapy with Lu-177 DOTATATE*

Abstract

Background/aim: To describe the role of baseline gallium (Ga)-68 DOTATATE positron emission tomography (PET)/computed tomography (CT) in the prediction of the response to peptide receptor radionuclide therapy (PRRT) using lutetium (Lu)-177 DOTATATE.Materials and methods: Analysis was made of baseline Ga-68 DOTATATE PET/CT images of 29 patients (17 females and 12 males; mean age: 50.7 ± 14.6 years) with metastatic neuroendocrine tumors who received PRRT with Lu-177 DOTATATE. Maximum standardized uptake values (SUVmax) of reference lesions and their ratios to physiological uptake organs were calculated. The relationship between these values and the radiological response was analyzed.Results: Partial response was observed in 8 (28%) patients, stable disease in 18 (62%) patients, and progressive disease in 3 (10%) patients. Mean SUVmax of reference lesions was calculated as 23.8 ± 20.5 (min-max: 5.1-87.3). There was no significant correlation between radiological responses and SUVmax of reference lesions and their ratios to other organs. Conclusion:Baseline Ga-68 DOTATATE PET/CT helps to show somatostatin receptor expression status and disease stage in patients who are candidates for PRRT. However, SUVs do not have a role in the prediction of treatment response.

PRRT: identikit of the perfect patient

“…Similar results were found by the same group in 2019, in their retrospective study where only panNETs were evaluated: SUV max/mean failed to predict PFS, whereas the intratumoral textural feature (TF) analysis, assessed by a baseline SSTR-PET, predicted response in terms of PFS [81]. The following studies also did not find any significant relationship between the response to PRRT and SUV max of reference lesions [26] (p 0.12), [73] (p = 0.25), [27] (p = 0.59). Regarding 18 F-FDG PET, all studies tend to divide patients in PET-positive and PET-negative, depending on a value of SUV max 2.5 or more, as an arbitrary cut off to consider a lesion positive for malignancy (see Table 3).…”

“…Concerning 68 Ga-DOTA-peptide PET, all studies assessed tumor standardized uptake value (SUV) as a quantitative parameter, to predict response to PRRT (see Table 2). Among eleven papers that analyze 68 Ga-PET, three papers did not find any significant result that attributes a predictive role to maximum SUV (SUV max ) during 68 Ga-PET ( [26,27,73]), two papers from the same group [80,81] identified other parameters besides SUV max , able to predict outcome of PRRT treatment, and six identified SUV max as a predictor of response to therapy [25,31,38,53,54,71]. All studies were performed on rather small NET series.…”

Targeted Radionuclide Therapy: New Advances for Improvement of Patient Management and Response

“…The level of uptake in tumour on the baseline, the PET scan has been explored as a predictor of response in SSTR-positive NETs with inconclusive evidence. 68 Ga-DOTATOC measured as standard uptake value (SUV) on baseline PET/CT was correlated with time to progression, however this relationship could not be confirmed in the patient cohort of Soydal et al [3]. As an alternative, the expression of SSTR quantified by SSTR-PET has been explored as a potential predictor of response to 177 Lu-DOTA-TATE.…”

64Cu-DOTATOC PET-CT in Patients with Neuroendocrine Tumors

“…It must be emphasized that regarding peptides used for PET imaging, there are still conflicting reports and no peptide has been concluded to be the optimal peptide for imaging of NETs. Despite the small number of heterogenous patients, which is a limitation of the study, it has been shown that baseline PET-CT with 68 Ga-DOTATATE helps to determine somatostatin receptor expression status and disease stage in patients, but SUV calculations do not necessarily have a role in the prediction of treatment response [26]. However, because of the long half-life of 64 Cu of 12.7 h, it is possible to perform images later than 1 h, e.g., either for dosimetric purposes or for any other logistical reasons in routine clinical work.…”