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SNMMI 2019: Peptide Receptor Radionuclide Therapy May Be Effective in High-Grade Neuroendocrine Neoplasms

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Key Points

  • The median progression-free survival rate for patients with grade 3 neuroendocrine neoplasms was 9.6 months, and the overall survival rate was 19.9 months.
  • Patients with a Ki-67 index less than or equal to 55% responded more favorably to the PRRT than others, with a median progression-free survival rate of 11 months and an overall survival rate of 22 months.
  • Patients with a good response and favorable outcome after PRRT were observed to have a relatively higher SUVmax with Ga-68–SSTR PET/CT imaging. Patients with no or minor 18F-FDG uptake responded well to PRRT, and the survival rates were significantly longer than for those with avid 18F-FDG uptake.

Peptide receptor radionuclide therapy (PRRT) has been shown to be safe and effective for patients with grade 3 neuroendocrine neoplasms, according to research presented at the 2019 Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI) and published by Zhang et al in The Journal of Nuclear Medicine.

Methods

“While numerous studies have demonstrated the effectiveness of PRRT in well-differentiated grade 1 and 2 neuroendocrine neoplasms, limited data has been reported on PRRT in grade 3 neuroendocrine neoplasms,” noted study author Richard P. Baum, MD, PhD, Chairman and Clinical Director at the Theranostics Center for Molecular Radiotherapy and Precision Oncology in Bad Berka, Germany. “Our study—which followed the largest cohort of [patients with] grade 3 neuroendocrine neoplasms for the longest period of time—aimed to assess the safety and efficacy of PRRT in terms of survival analysis. In addition, we evaluated the utility of positron-emission tomography (PET)/computed tomography (CT) in predicting long-term prognosis.”

In the study, 69 patients with various types of metastatic, progressive grade 3 neuroendocrine neoplasms received PRRT with lutetium Lu-177 dotatate and/or yttrium-90–labeled dotatate or dotatoc. For some patients, this therapy was a first-line treatment, but for the majority, PRRT was a second- or third-line treatment. Patients were followed for a median of 94.3 months, and progression-free survival and overall survival rates were calculated.

Results

The median progression-free survival rate for patients with grade 3 neuroendocrine neoplasms was 9.6 months, and the overall survival rate was 19.9 months. When taking into account the Ki-67 index, researchers found a significant difference between survival rates: patients with a Ki-67 index less than or equal to 55% responded more favorably to the PRRT than others, with a median progression-free survival rate of 11 months and an overall survival rate of 22 months.

“Compared to studies evaluating the efficacy of chemotherapy for [patients with neuroendocrine neoplasms] with a Ki-67 index less than or equal to 55%, PRRT has a longer overall survival rate—22 months vs 14 months,” the researchers said. “These results suggest that PRRT, rather than chemotherapy, may be a superior first-line therapeutic option in selected patients with a high level of somatostatin receptor (SSTR) expression and a Ki-67 index of less than or equal to 55%.”

In addition to tracking survival rates, researchers also performed response assessments with gallium Ga-68 somatostatin receptor PET/CT and fluorine-18 (F-18)-fluorodeoxyglucose (FDG) PET/CT. Patients with a good response and favorable outcome after PRRT were observed to have a relatively higher SUVmax with Ga-68–SSTR PET/CT imaging. Patients with no or minor F-18–FDG uptake responded well to PRRT, and the survival rates were significantly longer than for those with avid F-18–FDG uptake. In terms of stratifying patients, the mismatch pattern of low F-18–FDG uptake and high Ga-68–SSTR uptake was associated with a better long-term prognosis.

First author Jingjing Zhang, MD, PhD, and Dr. Baum noted in a press release, “Overall, our findings demonstrated that PRRT was tolerated well, without any significant adverse effects, and was effective in patients with grade 3 neuroendocrine neoplasms, even those for whom chemotherapy had failed. These findings provide the basis for the expansion of clinical indications of PRRT in the future.”

Disclosure: For full disclosures of the study authors, visit jnm.snmjournals.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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