Somatostatin receptor scintigraphy during treatment with lanreotide in patients with neuroendocrine tumors.

To investigate possible changes in somatostatin receptor expression during treatment with high dose lanreotide, eight patients with neuroendocrine tumors were investigated by [(111)In-DTPA-D-Phe1]-octreotide scintigraphy before and during treatment. The spleen-to-background ratio decreased in all patients, whereas tumor-to-background ratio revealed a heterogeneous pattern with an average increase of 50% (-79% to +1,087%). This finding indicates that lanreotide treatment may influence the binding of radioactively labeled somatostatin to the spleen, while changes in the binding to functioning somatostatin receptors in tumor cells are more complex and not clearly related to treatment.