NANETS2022 15th Annual Multidisciplinary NET Medical Symposium NANETS 2022 Clinical – Nuclear Medicine/Interventional Radiology/Imaging (16 abstracts)
Evaluation of 68Ga-DOTATATE PET After Two Cycles of Peptide Receptor Radionuclide Therapy (PRRT) in Neuroendocrine Tumors (NET)
Duan Heying 1 , Song Hong 1 , Ferri Valentina 1 , Fisher George 2 , Shaheen Shagufta 2 , Sha Jagruti 1 , Nguyen Judy 1 , Moradi Farshad 1 , Franc Ben 1 , Davidzon Guido 1 , Iagaru Andrei 1 & Mari Aparici Carina 1
1Department of Radiology, Division of Nuclear Medicine and Molecular Imaging, Stanford University, Stanford, CA; 2Department of Medicine, Division of Oncology, Stanford University, Stanford, CA.
Background: We aimed to evaluate the added information provided by 68Ga-DOTATATE PET after two cycles of peptide receptor radionuclide therapy (PRRT) in patients with somatostatin receptor (SSTR)-expressing neuroendocrine tumors (NET).
Methods: In this retrospective study, 105 patients (54 women and 51 men, 62.5±10.5-year-old) with progressive NET treated with at least two cycles of 177Lu-DOTATATE were included. All patients had 68Ga-DOTATATE PET (PET/CT or PET/MRI) at baseline, after two cycles, and upon completion of PRRT. RECIST and change in SSTR-density were used to evaluate the scans and assess treatment response. Change in tumor marker chromogranin A was recorded. Patients were surveyed regarding their stance on the additional scan midway through the treatment.
Results: All patients considered the additional 68Ga-DOTATATE PET contributing to their quality of life as it provided important peace of mind. After two PRRT cycles, 0/105 (0%) patients showed complete response (CR), 54/105 (51%) partial response (PR), and 40/105 (38%) had stable disease (SD) with agreement between RECIST and SSTR-density. In 11/105 (11%) patients RECIST and SSTR-density were discordant: progressive disease (PD) according to RECIST was seen in 11/11 patients, while evaluation of SSTR-density showed true progression in 4/11 and pseudo-progression in 7/11 patients. Follow-up imaging after completion of PRRT verified results from interim imaging: 4/11 had true progression while the other 7/11 patients showed PR. The pattern of pseudo-progression consisted in an up to 2 mm increase in size of known NET lesions, with or without central necrosis or new stranding, but no new lesions. The SSTR-density in these patients was stable or decreased when related to the liver. Chromogranin A was available in 37/105 patients. The change in chromogranin A did not positively correlate with response to treatment.
Conclusions: Our data show that a 68Ga-DOTATATE PET after two cycles of PRRT provides important reassurance for the patient about the status of the disease and response to treatment. No patient showed CR after two cycles of PRRT, clearing concerns about possible overtreatment. 68Ga-DOTATATE PET is more accurate in assessing treatment response after two cycles than RECIST, allowing continuation of treatment in patients with pseudo-progression. Change in tumor marker did not correlate well with response to treatment after two treatment cycles.
Abstract ID 21480
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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