Experience with Somatostatin Receptor Scintigraphy in the Management of Pulmonary Carcinoid Tumors

Background: Somatostatin receptor scintigraphy has been used widely for the evaluation of neuroendocrine tumors in the gastrointestinal tract. Its use for detecting and staging thoracic carcinoids is only sporadically reported. Objectives: To evaluate the possible roles of SRS in the man- agement of proven or suspected pulmonary carcinoids. Methods: We conducted a retrospective study of all patients undergoing SRS for known or suspected pulmonary carcinoids in a tertiary referral center during a 10 year period. During this period 89 patients underwent resection of pulmonary carcinoids and SRS was used for detection, staging or localization purposes in 8 of them (9%). Scans were labeled true positive, true negative, false positive, or false negative in comparison with histologic or follow-up results. Results: SRS was true positive in 6/6 lung locations; true positive in 2/8, true negative in 4/8 and false positive in 2/8 lymph node locations; and true positive in 1/8, true negative in 6/8 and false negative in 1/8 distant locations. The sensitivity, specificity, positive and negative predictive values and accuracy were 90%, 83%, 83%, 91% and 87% respectively. The scans were strongly positive in the tumors and involved lymph nodes. SRS correctly localized an occult secreting pulmonary carcinoid. Granulomatous and reactive lymph nodes showed increased uptake. SRS was accurate in ruling out distant metastases. Conclusions: SRS is effective for visualizing and localizing pulmonary carcinoids. It assists in the staging of these tumors by detecting lymph node involvement and confirming or ruling out distant metastases. Inflamatory areas in the lung or lymph nodes may be falsely positive.