Background:
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Ga-DOTATATE PET-CT (DOTATATE-PET) has higher sensitivity and positive predictive value than other studies, reason for which it has become the imaging modality of choice for Neuroendocrine tumor (NET) localization, but data on ACTH-secreting NET is scarce.
Case summary:
61 year old female with history of right hepatic lobe lipoma resection, T2DM (A1c 9.4%), HTN, and benign thyroid nodule that was evaluated for cushingoid features with facial and lower extremity edema, progressive generalized weakness, difficulty climbing stairs, 20 lbs weight loss and intermittent hypokalemia while on a diuretic plus three other antihypertensives over a six month period. ACTH-dependent hypercortisolism was confirmed with a non-suppressed ODST 11.27mcg/dL (normal <1.8), elevated 24 hr urine free cortisol 525 mcg/24h (RR 4.0-50.0, total volume 3.85 L, creatinine 0.92 g/24 hr), midnight salivary cortisol 1.13 mcg/dL(RR ≤0.09), and ACTH 122 pg/mL (RR 6-50). Additionally, plasma metanephrines were negative, aldosterone <1 ng/dl (RR ≤21) and renin activity 0.58 ng/mL/h (RR 0.25-5.82). Cushing’s disease was suspected since her 8am cortisol suppressed >50% after 8 mg dexamethasone (dexa) overnight (pre-dexa cortisol 33.78 mcg/dL, post-dexa cortisol 6.59 mcg/dL). However, MRI Sella did not show a pituitary adenoma and IPSS was compatible with Ectopic ACTH-secretion (EAS). CT chest, abdomen, pelvis with contrast did not reveal any frank lesion that could be the culprit of EAS. Octreoscan and FDG-PET were negative. DOTATATE-PET reported a mild focus of uptake on the medial aspect of the right upper lung lobe, thought to be a branching blood vessel since no anatomic lesion was seen on CT Chest that would correspond to the possible area of uptake. In the interim, she developed diffuse ecchymosis with worsening of her functional status, needing a walker and assistance with activities of daily living. She had several falls complicated by multiple lumbar compression fractures, rib, right pubic ramus and bilateral sacral insufficiency fractures for which she received reclast, a back brace and physical therapy. She was started on ketoconazole and titrated up, but due to rapid progression of her Cushing syndrome over five months without an identifiable source of EAS, the decision was made to proceed with bilateral adrenalectomy and perform surveillance imaging to identify growth of a possible occult NET.
Conclusion:
In our case, DOTATATE-PET did not help to localize an ACTH-secreting NET, suggesting that the sensitivity of this study might not be as good as reported for other types of NET. Therefore, Occult EAS remains a diagnostic challenge and clinicians may resort to bilateral adrenalectomy for permanent biochemical control and serial CT imaging to detect an incipient NET.
