Endocrine Abstracts

JOINT3423

Introduction: Pheochromocytomas (PHEOs) and paragangliomas (PGLs), collectively known as PPGLs, are rare endocrine tumors with significant clinical variability. Around 10–15% of PHEOs and 35–40% of PGLs exhibit metastatic behavior. Due to their heterogeneity, treatment must be tailored to each patient individually.

Methods: This study aim to describe the general characteristics, treatments strategies, and response in a cohort of 49 patients with metastatic PPGLs. It is a retrospective study (2010–2024) conducted at two reference NET centers in Spain.

Results: Among the 49 patients, 51% with a mean age of 52.7 years (S.D.:8.4). The mean age at diagnosis was 40.9 years (S.D. 19.1). PHEO was the primary tumor in 25 patients. The most common reasons leading to diagnosis were incidental findings (23.1%), hypertension (20.5%), cervical mass (15.4%), and abdominal pain (15.4%). A total of 51% of cases were functional, with the majority exhibiting a noradrenergic phenotype (76%). At diagnosis, 44.9% of patients had metastases, with the most frequent metastatic sites being bone (32.7%), lymph nodes (26.5%), liver (22.4%), and lungs (14.3%). Systemic treatment was not administered to 14.3% of patients. Among those treated, the main indications were disease progression (PD)(59.5%), high tumor burden (31%), and tumor functionality (9.5%). Most patients (43.2%) received only one line of treatment. The remaining patients received more than one line: 23.8% received two, 16.7% three, 9.5% four, 4.8% five, and 4.8% seven First-line treatments included somastotin analogs (SSA)(40.5%), radionuclide therapy (33.3%), and chemotherapy (26.2%). No significant differences were observed between the reason for treatment initiation and the choice of first-line therapy (P=0.316). However, differences were found between the reason for starting treatment and the best radiological response achieved (P=0.01), with a higher partial response (PR) rate in patients with a high tumor burden compared to those with disease progression (38.4% vs 8%). PR was seen in 27.2% of the patients receiving chemotherapy and 28.5% of those treated with radioligands, compared to 5.88% with SSA (P=0.14). After first-line treatment, 63.1% of patients experienced disease progression, with a median progression-free survival of 25.6 months (S.D. 21.2). Significant differences were observed depending on the type of treatment received (SSA:11 months, radionuclide therapy:16.4 months, chemotherapy:7.2 months)(P=0.02).

Conclusions: The most common indication for initiating systemic treatment in PPGLs is radiological disease progression. However, initial tumor burden appears to be the most influential factor in predicting radiological response. Prospective studies are needed to determine the optimal timing for initiating systemic treatment in PPGLs.