Tumor detection rates in screening of individuals with SDHx-related hereditary paraganglioma–pheochromocytoma syndrome

Purpose: Minimal data exist regarding the efficacy of screening protocols for individuals with SDHx germline pathogenic variants with Hereditary Paraganglioma-Pheochromocytoma Syndrome. This study aimed to evaluate the SDHx-related tumor detection rate in individuals undergoing clinical screening protocols. Methods: A multi-center retrospective longitudinal observational study was conducted. Individuals with germline SDHx pathogenic variants underwent clinical whole-body imaging and biochemical testing. Results: 263 individuals with SDHx germline pathogenic variants completed 491 imaging screens. Individuals with SDHB germline pathogenic variants were most common (n=188/263, 72%), followed by SDHD (n=35/263, 13%) and SDHC (n=28/263, 11%). SDHx-related tumors were found in 17% (n=45/263) of the cohort. Most SDHx-related tumors were identified on baseline imaging screen (n=39/46, 85%). Individuals with SDHD pathogenic variants had the highest tumor detection rate (n=14/35, 40%). Of imaging screens identifying SDHx-related paraganglioma/pheochromocytoma, 29% (n=12/41) had negative biochemical testing. Secondary actionable findings were identified in 15% (n=75/491) of imaging screens. Conclusion: Current SDHx screening protocols are effective at identifying SDHx-related tumors. Tumor detection rates vary by SDHx gene and screening has the potential to uncover actionable secondary findings. Imaging is an essential part of the screening process as biochemical testing alone does not detect all disease.