Utility of various functional and anatomic imaging modalities for detection of ectopic adrenocorticotropin-secreting tumors.

CONTEXT

Because ectopic ACTH-secreting (EAS) tumors are often occult, improved imaging is needed.

OBJECTIVE

Our objective was to evaluate the utility of [(111)In-DTPA-d-Phe]pentetreotide scintigraphy [octreotide (OCT)] imaging at 6 mCi [low OCT (LOCT)] and 18 mCi [high OCT (HOCT)], [(18)F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) and [(18)F]l-3,4-dihydroxyphenylalanine (F-DOPA)-PET scans, computed tomography (CT), and magnetic resonance imaging (MRI).

DESIGN AND SETTING

The study was a prospective evaluation at a clinical research center.

PATIENTS

Forty-one subjects participated, 30 (17 female) with resected EAS tumors and 11 (three female) with occult EAS, based on inferior petrosal sinus sampling results and imaging studies.

INTERVENTION

INTERVENTION included CT and MRI of neck, chest, abdomen, LOCT (with or without HOCT) and FDG- or F-DOPA-PET without CT every 6-12 months.

MAIN OUTCOME MEASURE

Tumor identification was the main outcome measure.

RESULTS

Most recent results were analyzed. Eighteen patients had tumor resected on the first visit; otherwise, surgery occurred 33 +/- 25 (9-99) months later. Tumor size was 1.9 +/- 1.7 (0.8-8.0) cm; 83% were intrathoracic. CT, MRI, LOCT, HOCT, FDG-PET, and F-DOPA-PET had sensitivities per patient of 93% [95% confidence interval (CI) = 79-98%], 90% (95% CI = 74-96%), 57% (95% CI = 39-73%), 50% (95% CI = 25-75%), 64% (95% CI = 35-85%), and 55% (95% CI = 28-79%) and positive predictive values (PPV) per lesion of 66, 74, 79, 89, 53, and 100%, respectively. LOCT and PET detected only lesions seen by CT/MRI; abnormal LOCT or F-DOPA-PET improved PPV of CT/MRI. By modality, the fraction of patients with one or more false-positive findings was 50% by CT, 31% by MRI, 18% by L/HOCT, and 18% by FDG-PET. Eight occult EAS patients had 64 +/- 58 (9-198) months follow-up; others had none.

CONCLUSIONS

High sensitivity and PPV suggest thoracic CT/MRI plus LOCT scans for initial imaging, with lesion confirmation by two modalities.