Somatostatin receptor scintigraphy in metastatic breast cancer patients

The purpose of this study was to evaluate the efficacy of somatostatin receptor scintigraphy (SRS) in imaging metastases in patients with advanced breast cancer (BC), and assess the relationship between exposure to chemotherapy and hormonotherapy with overexpression of somatostatin receptor (SS-R) on the breast cancer cell surface. Twelve patients with metastatic breast cancer were intravenously (i.v.) injected with In-111 pentatreotide (120 MBq). Early and later images were obtained with a double-head gamma camera equipped with medium-energy collimators. SPECT was performed when needed. Imaging results were compared with computed tomography and bone scan. Uptake levels were evaluated by site-specific visual analysis. Metastatic breast cancer can be visualized with SRS. Global sensitivity of imaging was 80% and specificity for correct prediction of tumor absence was 100%. Sensitivity was significantly higher for bone and lung metastases. SRS results related to the expression of SS-R on metastatic cell surfaces did not evidence a relationship with the biologic characteristics of the primary BC and drug exposure. In our series, SRS quantitative analysis demonstrated that tumor metastases differ greatly in uptake levels. Fifteen percent of metastatic sites in our series showed strong uptake. Our data support the important specificity of SRS in identifying BC metastases, mostly in cases of bone and lung disease, as well as the role of SRS in predicting responsiveness of metastatic BC cells to treatment with somatostatin analogues (SS), when SS-Rs are overexpressed on cell surfaces. If our results are confirmed in large scale studies, SRS shows the potential to treat selected patients with overexpressed SS-R on their tumoral cells with designed target therapies with SS analogue.