Head-to-head comparison of 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT in localizing tumors with ectopic adrenocorticotropic hormone secretion: a prospective study

Drug conjugates for the treatment of lung cancer: from drug discovery to clinical practice

A drug conjugate consists of a cytotoxic drug bound via a linker to a targeted ligand, allowing the targeted delivery of the drug to one or more tumor sites. This approach simultaneously reduces drug toxicity and increases efficacy, with a powerful combination of efficient killing and precise targeting. Antibody‒drug conjugates (ADCs) are the best-known type of drug conjugate, combining the specificity of antibodies with the cytotoxicity of chemotherapeutic drugs to reduce adverse reactions by preferentially targeting the payload to the tumor. The structure of ADCs has also provided inspiration for the development of additional drug conjugates. In recent years, drug conjugates such as ADCs, peptide‒drug conjugates (PDCs) and radionuclide drug conjugates (RDCs) have been approved by the Food and Drug Administration (FDA). The scope and application of drug conjugates have been expanding, including combination therapy and precise drug delivery, and a variety of new conjugation technology concepts have emerged. Additionally, new conjugation technology-based drugs have been developed in industry. In addition to chemotherapy, targeted therapy and immunotherapy, drug conjugate therapy has undergone continuous development and made significant progress in treating lung cancer in recent years, offering a promising strategy for the treatment of this disease. In this review, we discuss recent advances in the use of drug conjugates for lung cancer treatment, including structure-based drug design, mechanisms of action, clinical trials, and side effects. Furthermore, challenges, potential approaches and future prospects are presented.

Site-specific performance of 68Ga-DOTATATE PET/CT in detecting tumors with ectopic adrenocorticotropic hormone secretion

Objective

The aim of this study was to assess the detection ability of ⁶⁸Ga-DOTATATE in pulmonary versus extrapulmonary tumors with ectopic adrenocorticotropic hormone secretion (EAS).

Methods

Images of ⁶⁸Ga-DOTATATE PET/CT from 74 patients with suspected EAS were retrospectively reviewed. EAS tumors were confirmed in 39 patients through surgical resection or biopsy. Image findings were compared with the histopathological results.

Results

EAS tumors were pathologically confirmed via surgery or biopsy in 39 patients. Among those 39 patients, 25 were with pulmonary neuroendocrine tumors (NETs), and the remaining 14 were with extrapulmonary NETs. ⁶⁸Ga-DOTATATE PET/CT correctly identified the tumor in 26 patients, rendering an overall detection rate of 66.7%. On a site-based analysis, ⁶⁸Ga-DOTATATE PET/CT correctly identified the EAS tumor in 13 of 25 patients with pulmonary NETs, yielding a detection rate of 52%; for the 14 patients with extrapulmonary NETs, ⁶⁸Ga-DOTATATE PET/CT correctly identified the EAS tumor in 13, yielding a detection rate of 92.9%. The detection rate of ⁶⁸Ga-DOTATATE was significantly higher in extrapulmonary NETs than in pulmonary NETs (92.9%% vs. 52%, P = 0.013). For the 13 patients with positive pulmonary NETs, the tumor SUVmax ranged from 1.1 to 7.4 with an average SUVmax of 3.1 ± 2.1. For the 13 patients with positive extrapulmonary NETs, the tumor SUVmax ranged from 2.7 to 21.8 with an average SUVmax of 9.9 ± 6.3. The tumor SUVmax was significantly higher in extrapulmonary tumors than pulmonary tumors (P = 0.015). The tumor size was smaller in pulmonary tumors than in extrapulmonary tumors, while the difference was not significant (P = 0.516).

Conclusion

⁶⁸Ga-DOTATATE showed site-specific difference in detecting tumors with EAS secretion. Specifically, ⁶⁸Ga-DOTATATE performed better in the extrapulmonary EAS tumors than in pulmonary ones with both higher detection rate and uptake. Combination of anatomic imaging techniques are necessary for the correct diagnosis of pulmonary EAS tumors.

Pediatric Ectopic Cushing Syndrome Caused by Hepatic Neoplasms: A Case Report and Systematic Review

Ectopic adrenocorticotropic hormone (ACTH) syndrome (EAS) is rare in children, and localizing the source of EAS is often challenging. Here, we report EAS in an adolescent boy who presented with Cushingoid features and had endogenous ACTH-dependent hypercortisolism on hormonal evaluation. Abdominal ultrasound and CT revealed a hepatic lesion with characteristics suggestive of hemangioma, whereas the lesion was tracer non-avid on ⁶⁸Ga-DOTANOC positron emission tomography/CT. A regional sampling of ACTH was done to confirm the hepatic lesion as the source of EAS, and a definitive ACTH gradient was observed between the hepatic vein and the right internal jugular vein. Further, a preoperative biopsy of the lesion revealed a small round cell tumor with positive immunostaining for ACTH and synaptophysin, suggestive of a neuroendocrine tumor. The patient was managed with partial hepatectomy, resulting in hormonal and clinical remission of Cushing syndrome. In a systematic review of pediatric EAS due to primary hepatic tumors (n = 11), calcifying nested stromal epithelial cell tumors were the most common. EAS-associated hepatic tumors were larger (≥10 cm) except benign primary hepatic neuroendocrine tumors (PHNET). The latter were misdiagnosed as hemangioma in two cases by anatomical imaging but correctly diagnosed by somatostatin receptor scintigraphy. Hepatic tumors causing EAS in children required extensive resection, except benign PHNET. Nevertheless, all benign tumors with an uncomplicated perioperative course demonstrated disease-free survival over a median follow-up period of two years.

Ectopic adrenocorticotrophic hormone syndrome secondary to treatment-related neuroendocrine differentiation of metastatic castrate-resistant prostate cancer

Summary

A 64-year-old man with progressive metastatic castrate-resistant prostate adenocarcinoma presented with recurrent fluid overload, severe hypokalaemia with metabolic alkalosis and loss of glycaemic control. Clinical features were facial plethora, skin bruising and proximal myopathy. Plasma adrenocorticotrophic hormone (ACTH), serum cortisol and 24-h urinary cortisol levels were elevated. Low-dose dexamethasone failed to suppress cortisol. Pituitary MRI was normal and 68Gallium-DOTATATE PET-CT scan showed only features of metastatic prostate cancer. He was diagnosed with ectopic ACTH syndrome secondary to treatment-related neuroendocrine prostate cancer differentiation. Medical management was limited by clinical deterioration, accessibility of medications and cancer progression. Ketoconazole and cabergoline were utilised, but cortisol remained uncontrolled. He succumbed 5 months following diagnosis. Treatment-related neuroendocrine differentiation of prostate adenocarcinoma is a rare cause of ectopic ACTH syndrome.

Learning points

Neuroendocrine differentiation following prostate adenocarcinoma treatment with androgen deprivation has been described. Ectopic adrenocorticotrophic hormone (ACTH) syndrome should be considered where patients with metastatic prostate cancer develop acute electrolyte disturbance or fluid overload. Ketoconazole interferes with adrenal and gonadal steroidogenesis and can be used in ectopic ACTH syndrome, but the impact may be insufficient. Inhibition of gonadal steroidogenesis is favourable in prostate cancer. More data are required to evaluate the use of cabergoline in ectopic ACTH syndrome. Ectopic ACTH syndrome requires prompt management and is challenging in the face of metastatic cancer.

Usefulness of 68 Ga-Pentixafor PET/CT on Diagnosis and Management of Cushing Syndrome

PURPOSE

This pilot study investigated the performance of C-X-C motif chemokine receptor 4 (CXCR4) molecular imaging ( 68 Ga-pentixafor PET/CT) in Cushing syndrome (CS) and the correlation between CXCR4 signaling interactions and glucose metabolism in adrenocorticotropin-cortisol pathway.

METHODS

We retrospectively evaluated 31 patients (16 patients with CS and 15 patients with nonfunctioning pituitary or adrenal adenomas). All patients underwent 68 Ga-pentixafor PET/CT, and 11 with pituitary adenoma also underwent 18 F-FDG PET/CT. The diagnosis accuracy of 68 Ga-pentixafor PET/CT was calculated. The correlation between radiouptake along the pituitary-adrenal axis and hormone levels was calculated.

RESULTS

Patients with Cushing disease characterized a focal uptake in adrenocorticotropic hormone-producing pituitary adenoma (ACTH-PA). In ACTH-independent CS, there was increased uptake of 68 Ga-pentixafor in adrenal lesions but not in the pituitary fossa. The nonfunctioning pituitary or adrenal adenomas showed negative 68 Ga-pentixafor signal. The one patient with metastatic ectopic ACTH syndrome had multiple 68 Ga-pentixafor-avid lesions. Using the threshold of SUV max >8.5 in the adrenal lesions, the sensitivity and specificity of 68 Ga-pentixafor PET/CT to diagnose cortisol-producing adenoma were 100% and 84.9%. A cutoff SUV max value of 3.0 on 68 Ga-pentixafor PET/CT had 100% sensitivity and specificity for differentiating ACTH-PA. The corresponding hormone level was significantly correlated with uptake of 68 Ga-pentixafor in pituitary adenoma and adrenal tissue but not with glucose metabolism.

CONCLUSION

We have characterized the performance of 68 Ga-pentixafor in different subtypes of CS. 68 Ga-pentixafor PET/CT is promising in the differential diagnosis of both ACTH-independent and ACTH-dependent CS. Activated CXCR4 molecular signaling along the pituitary-adrenal axis was found in patients with Cushing disease.

Pituitary adenoma & nuclear medicine: Recent outcomes and ongoing developments

In order to explore pituitary adenoma (PA), magnetic resonance imaging (MRI) remains the cornerstone. However, there are some limitations and MRI can be non-conclusive. The development of additional imaging modalities like nuclear medicine explorations may help to confirm PA diagnosis, guide management and follow up. Nuclear medicine uses radiopharmaceuticals for imaging with single photon emission computed tomography (SPECT), or positron emission tomography (PET), coupled to CT scan. Radiopharmaceuticals products target specific cellular elements which allow to explore several biological pathways. Nuclear medicine may also be used for therapeutic purposes and recent developments of approach based on Peptide Receptor Radionuclide Therapy (PRRT) for treatment of aggressive PA and pituitary carcinoma will be reviewed. Several radiotracers have been studied in the context of PA, and the aim of this paper is to discuss their respective performances and clinical interest.

Comparison of diagnostic efficacy of 18F-FDG PET/CT and 68Ga-DOTANOC PET/CT in ectopic adrenocorticotropic hormone syndrome

PURPOSE

Fluorine-18 (¹⁸F)-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and gallium-68 (⁶⁸Ga)-somatostatin analog (SSA) PET/CT imaging have been increasingly used in ectopic adrenocorticotropic hormone syndrome (EAS); however, the diagnostic efficacies of these two methods in patients with EAS remain unclear. Our study aimed to compare the diagnostic efficacies of ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTANOC PET/CT in EAS.

METHODS

The clinical and imaging data of 68 patients with EAS who underwent ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTANOC PET/CT examinations from December 2016 to April 2021 were analyzed retrospectively, and the diagnostic efficacies of these methods were compared.

RESULTS

In 37 cases, imaging was performed to locate the primary tumor lesion (localization group), and in 31 to evaluate tumor load or metastasis (staging group). Primary tumors were detected in 48.65% (18/37) of the localization group patients. According to scan-based analysis, the tumor lesion detection rates and false positive rates of ¹⁸F-FDG PET/CT imaging and ⁶⁸Ga-DOTANOC PET/CT imaging were 18.92% vs. 45.95% (p < 0.05) and 21.62% vs. 2.70% (p < 0.05) respectively. For lesion-based analysis, the tumor lesion detection rates and false positive rates were 24.13% vs. 58.62% (p >0.05) and 31.04% vs. 3.45% (p < 0.05). In 90.32% (28/31) of the staging group patients, 286 of 292 lesions were confirmed as tumor lesions. Based on scan analysis, the detection rates and false positive rates of ¹⁸F-FDG PET/CT imaging and ⁶⁸Ga-DOTANOC PET/CT imaging were 83.87% vs. 67.74% (p > 0.05) and 12.90% vs. 9.68% (p > 0.05) respectively. Based on lesion analysis, the detection rate and false positive rates were 93.84% vs. 54.80% (p < 0.05) and 1.37% vs. 1.03%(p > 0.05).

CONCLUSION

⁶⁸Ga-DOTANOC PET/CT imaging may be more suitable than ¹⁸F-FDG PET/CT for identifying the primary tumor in patients with EAS, while ¹⁸F-FDG PET/CT may be more advantageous than ⁶⁸Ga-DOTANOC PET/CT for patients with suspected metastasis.