CONTEXT: Indium-labeled somatostatin formed the first wave of cell-surface receptor scintigraphy in the mid-1990s. While its value was limited to diagnosing and staging neuroendocrine tumors (NET), the molecularly based agent has proved superior to CT and MR in these roles. Dr. Eric P. Krenning of Erasmus University Medical Center in the Netherlands has expanded its role by labeling somatostatin with therapeutic radionuclides, producing a peptide-receptor therapy.
RESULTS: More than 400 patients with NET-expressing somatostatin receptors have undergone radiotherapy at the Erasmus hospital since 1992. The standard protocol employs a somatostatin targeting agent and either lutetium-177 or yttrium-90 beta-particle emitters for therapy. The approach has proved increasingly effective at shrinking tumors, especially with the third-generation analog lutetium-177 DOTA-Tyr3 octreotide, according to Krenning.
Treatments involving three or four sessions over eight to nine weeks have cut the volume of tumors in more than half for 20% to 30% of patients. On average, the effect of the second-generation analog lasts for at least 36 months, helping to reduce fatigue, insomnia, and pain. More than half of the patients treated with the second-generation analog have survived at least five years.
IMPLICATIONS: Although molecular imaging is billed as the next big thing in radiology, it has had a decade-long influence on the diagnosis, staging, and treatment of neuroendocrine tumors. Data suggest that patients receiving somatostatin receptor-guided therapy have fewer symptoms and longer survival than patients treated with chemotherapy. Krenning reported his results at the Society for Molecular Imaging meeting in September.