40462327

Targeted Detection of Recurrence and Metastasis in Adrenocortical Carcinoma: A Novel Approach Using 99mTc-FAPI-46 SPECT/CT Imaging

Nasrin Raeisi, MD,* Amin Saber Tanha, MD,* Ehsan Soltani, MD,¡ Kamran Aryana, MD,* and Somaye Barashki, MD*

Abstract: We present a case of a 73-year-old man with a history of adrenocortical carcinoma (ACC) who underwent multiple surgeries and treatments for recurrent and metastatic lesions. The patient underwent a 99mTc-FAPI-46 scan, which revealed FAPI uptake in all tumoral masses detected on contrast-enhanced CT scans and subsequent laparotomy, with favorable target-to-background ratios. Our experience suggests that 99mTc-FAPI-46 SPECT/CT may be a valuable complementary diag- nostic modality for ACC, especially when PET/CT is not available. This case highlights the importance of comprehensive evaluation and con- sideration of other diagnostic modalities in the management of ACC, given the potential of FAPI-based imaging agents.

Key Words: adrenocortical carcinoma, 99mTc-FAPI-46 SPECT/CT, diagnostic imaging, local recurrence, metastatic carcinoma

(Clin Nucl Med 2025;50:e435-e436)

Received for publication September 30, 2024; accepted December 22, 2024.

From the *Nuclear Medicine Research Center, Mashhad University of Medical Sciences (MUMS); and ¡Surgical Oncology Research Center, Mashhad University of Medical Sciences (MUMS), Mash- had, Iran.

Conflicts of interest and sources of funding: none declared.

Correspondence to: Somaye Barashki, MD, Nuclear Medicine Research Center, Mashhad University of Medical Science, Ahmadabad St, Mashhad 91766-99199, Iran. E-mails: barashkiS@mums.ac.ir, somaye.barashki87@gmail.com.

Copyright @ 2025 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/RLU.0000000000005734

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FIGURE 1. A 73-year-old man, diagnosed with adrenocortical carcinoma (ACC) 18 years prior, underwent curative left nephrectomy and adrenalectomy for debilitating abdominal pain without hormonal dysregulation symptoms. Immunohistochemical (IHC) analysis of the tumor revealed positivity for Cytokeratin, Vimentin, and Synaptophysin, while staining for $100 and Chromogranin was negative. Following complete resection of the primary tumor, he was placed on active surveillance. During a routine follow-up 8 years later, a para- aortic mass appeared, which was biopsied and confirmed as metastatic ACC. The mass was resected, followed by mitotane and chemotherapy with etoposide and cisplatin. He continued on routine follow-up for another 10 years until an enlarging hypoechoic nodule was detected in the left upper quadrant of the abdomen on recent 2-year sonographic assessments, suspicious for local recurrence. A contrast-enhanced abdominopelvic CT scan (A) revealed multiple lesions: a mass adhered to the jejunal loop in the left upper quadrant of the abdomen (yellow arrow), a bulky conglomerated lymph node in the retro-pancreatic space (asterisk), a mass adhered to the internal oblique muscle on the left side of the abdomen (blue arrow), and a smaller nodule adhered to the left rectus abdominis muscle (red arrow). An ultrasound-guided core-needle biopsy of the mass adhered to the left rectus abdominis muscle suggested metastatic carcinoma. IHC analysis was positive for Synaptophysin, Inhibin, and Cytokeratin, and negative for MelanA and PAX8, confirming adrenocortical carcinoma as the origin. In the trial setting, a 99mTc-FAPI-46 scan was conducted, revealing FAPI uptake in all tumoral masses detected on the contrast-enhanced CT scan (B), discernible on the whole-body FAPI scan (C) and more prominently visualized on the maximum intensity projection (MIP) image (D). Finally, the patient underwent laparotomy, the tumoral masses were resected, and the pathologic evaluation confirmed the initial biopsy results. Adrenocortical carcinomas (ACCs) are rare, with an incidence of 0.7-2 per million, and exhibit a bimodal age distribution, peaking in childhood and the fourth to fifth decades of life. For localized, nonfunctional ACC with margin-free resection, follow-up imaging is scheduled every 12 weeks to 12 months for up to 5 years, and then as clinically indicated, using chest CT scans (with or without contrast) and abdominal CT or MRI scans with contrast.1,2 In ACC, 18F-FDG PET/CT has been shown to be a valuable tool in assessing the overall extent of disease and detecting metastases, thereby informing patient management. However, it is essential to note that false-negative results have been reported in ~11% of cases, highlighting the need for comprehensive evaluation and consideration of other diagnostic modalities.3-7 While Kaplan et al8 have demonstrated the superiority of 18F-FDG PET/CT over 68Ga-FAPI-04 PET/CT in detecting recurrent and metastatic lesions in a patient with ACC, previous studies revealed that 68Ga-DOTA.SA.FAPI emerged as a highly effective diagnostic agent for ACC, exhibiting comparable performance to 18F-FDG PET/CT.9,10 Our experience with 99mTc-FAPI-46 SPECT/CT showed comparable detection rates to contrast-enhanced CT and favorable target-to-background ratios, suggesting its potential as a complementary diagnostic modality for ACC, especially when PET/CT is not available.

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