In combination with FDG PET/CT, Ga-DOTATATE PET/CT can noninvasively assess tumor heterogeneity, especially in G2 and G3 NETs, for personalized management of patients.

Gastroenteropancreatic neuroendocrine tumors (GEPNETs) are indolent neoplasms presenting unpredictable and unusual biologic behavior that causes many clinical challenges. Tumor size, existence of metastasis, and histopathologic classification remain incapable in terms of treatment decision and prognosis estimation. This study aimed to compare 68 Ga-DOTATATE and 18 F-FDG PET/CT in GEPNETs and to investigate the relation between the complementary PET/CT results and histopathologic findings in the management of therapy, particularly in intermediate-grade patients. Methods: The relation between complementary 68 Ga-DOTATATE and 18 F-FDG PET/CT results of 27 GEPNET patients (mean age, 56 y; age range, 33-79 y) and histopathologic findings was evaluated according to grade and localization using standardized maximum uptake values and Ki67 indices. Grade 2 (G2) patients were further evaluated in 2 groups as G2a (3%-9%) and G2b (10%-20%) according to Ki67 indices. Results: The sensitivity of 68 Ga-DOTATATE and 18 F-FDG PET/CT was 95% and 37%, respectively, and the positive predictive values were 93.8% and 36.2%, respectively. The sensitivity in detecting liver metastasis, lymph nodes, bone metastasis, and primary lesion was 95%, 95%, 90%, and 93% for 68 Ga-DOTATATE and 40%, 28%, 28%, and 75% for 18 F-FDG, respectively. Statistically significant differences were found between grades 1-2, 2a-2b, and 1-2b with respect to 68 Ga-DOTATATE PET/CT as well as between 1-2a and 1-2b with respect to 18 F-FDG PET/CT. However, no statistical differences were found between 1 and 2a (P . 0.05) for 68 Ga-DOTATATE and 2a and 2b (P 5 0.484) for 18 F-FDG. The impact of the combined 18 F-FDG and 68 Ga-DOTATATE PET/CT on the therapeutic decision was 59%. Conclusion: Combined 68 Ga-DOTATATE and 18 F-FDG PET/ CT is helpful in the individual therapeutic approach of GEPNETs and can overcome the shortcomings of histopathologic grading especially in intermediate-grade GEPNETs.

(68)Ga-DOTATATE has high T/B ratio with physiological biodistribution comparable to its counterparts. However, the presence of SSTRs in benign and malignant lesions unrelated to NET may be challenging in interpretation particularly where the physiological uptake is variable.

In the present report, strong relationships were detected between the negativity of ER, overexpression of c-erbB-2, tumor grade, tumor size, histopathology, axillary lymph node involvement and SUVmax values. Accordingly, we believe that SUVmax values obtained with (18)F-FDG PET/CT may provide some information about tumor biology of breast cancer.

Objectives This study is set out to estimate the radiation-absorbed doses to normal organs and tumor tissue using low-dose 177Lu-FAPI04 dosimetry to determine the safety and theranostic potential of fibroblast activation protein–targeted radionuclide therapy. Patients and Methods Four patients with metastatic advanced-stage cancer were administered low-dose 177Lu-FAPI04 for dosimetry measurements. Data acquisition for dosimetry of normal organs and tumors was performed by whole-body and 3D SPECT/CT imaging at 4, 24, 48, and 96 hours after administering 177Lu-FAPI04. Blood samples were drawn at 5, 15, 30, 60, 60, 120, and 180 minutes, and at 24, 48, and 96 hours for bone marrow dosimetry calculations. Results Mean absorbed doses per megabecquerel were 0.25 ± 0.16 mGy (range, 0.11–0.47 mGy), 0.11 ± 0.08 mGy (range, 0.06–0.22 mGy), and 0.04 ± 0.002 mGy (range, 0.04–0.046 mGy) for kidneys, liver, and bone marrow, respectively. The respective maximum estimated amount of radioactivity to reach radiation-absorbed dose limits were 120.9 ± 68.6 GBq, 47.5 ± 2.8 GBq, 397.8 ± 217.1 GBq, and 52.4 ± 15.3 GBq for kidneys, bone marrow, liver, and total body. The mean absorbed dose per megabecquerel was 0.62 ± 0.55 mGy for bone metastases, 0.38 ± 0.22 mGy for metastatic lymph nodes, 0.33 ± 0.21 mGy for liver metastases, and 0.37 ± 0.29 for metastatic soft tissue. The maximum absorbed dose in a tumor lesion was 1.67 mGy/MBq for bone, 0.6 mGy/MBq for lymph node, 0.62 mGy/MBq for liver, and 1 mGy/MBq for soft tissue. Conclusions The mean absorbed dose to organs at risk with 177Lu-FAPI04 is reasonably low, allowing for low tumor-absorbed dose rates by administering a higher dose. Further research on optimizing therapeutic efficacy and using alternative radioisotopes is necessary, along with an individualized dosimetric approach.