Background: Small cell lung cancer (SCLC) tumors have neuroendocrine features. In vitro and in vivo studies have demonstrated that 50%-75% of SCLC tumors express receptors for somatostatin. This might enable in vivo localization of the primary tumor and its metastases by using scintigraphy with a radiolabeled somatostatin analogue, such as octreotide.
Purpose and methods: The efficacy of scanning with In-111 labeled octreotide (octreotide scan) was studied in the staging of SCLC patients and compared with the results of conventional staging (liver ECHO, bone scintigraphy, MRI of the brain, spine, and pelvis). Imaging was performed in 29 patients with histologically confirmed SCLC at 4, 24, and 48 hours after intravenous injection of 185 MBq In-111 octreotide.
Results: In 24 of 29 patients, the primary tumor was visualized. In these 24 patients, 26 metastases were demonstrated with conventional staging, of which only nine were visualized with octreotide scan. Octreotide scans showed two metastases in the brain that were not visualized by MRI. In the other five patients, five metastases were demonstrated with conventional staging. Only two of these were detected with octreotide scan. However, octreotide scan did show a further metastasis in the brain that was not visualized by MR imaging.
Conclusion: Octreotide imaging has a limited use in the detection of SCLC metastases compared to conventional staging. It might have some specific value in the detection of brain involvement in patients with limited disease.