SDHB-Associated Pheochromocytomas: What is Their Clinical Behavior?

Area of Science:

• Endocrinology
• Oncology
• Genetics

Background:

• Germline pathogenic variants in succinate dehydrogenase subunit B (SDHB) are linked to paraganglioma/pheochromocytoma syndrome type 4 (PGL-4).
• SDHB-associated pheochromocytomas (PCC) are considered rare, with limited data on their clinical behavior.

Purpose of the Study:

• To characterize the clinical behavior of SDHB-associated pheochromocytomas (PCC).
• To analyze disease-free survival, progression, and overall survival in patients with SDHB-associated PCC.

Main Methods:

• Retrospective review of patients treated for SDHB-associated PCC between 1993 and 2023 at a tertiary cancer center.
• Collection and analysis of clinical and demographic variables, including survival outcomes.
• Assessment of treatment modalities, recurrence rates, and metastatic patterns.

Main Results:

• 18% of 90 identified SDHB carriers (n=16) were diagnosed with PCC, all unilateral.
• 25% of patients presented with distant metastasis (DM) at diagnosis; bone was the most common site (100%).
• Recurrence occurred in 77% of patients, with no significant difference between open resection and minimally invasive surgery (MIS).

Conclusions:

• SDHB-associated PCC, diagnosed in 18% of carriers, is often unilateral but presents with advanced and recalcitrant disease.
• The majority of SDHB-associated PCCs were MIBG positive, indicating potential for targeted imaging and therapy.
• Further research is necessary to fully elucidate the clinical behavior and optimize management strategies for PCC in PGL-4.