Outcomes of SDHB pathogenic variant carriers: A systematic review and meta-analysis.

CONTEXT:Carriers of germline pathogenic variants (PV) in succinate dehydrogenase type B (SDHB) are at increased risk of developing pheochromocytomas and paragangliomas (PPGL). Understanding their outcomes can guide recommendations for risk assessment and early detection. OBJECTIVE:We performed a systematic review and meta-analysis of the following outcomes in SDHB PV carriers: age-specific risk of developing tumors, metastatic progression, second primary tumor development, and mortality. MATERIALS AND METHODS:Pubmed, MEDLINE and EMBASE were searched. Sixteen studies met the inclusion criteria and were sorted into four outcome categories: age-specific penetrance, metastatic disease, risk of second tumour and mortality. We assessed heterogeneity and performed a meta-analysis across studies using a random effects model with the DerSimonian and Laird method. RESULTS:Penetrance of PPGL for non-proband/non-index SDHB PV carriers by age 20 was 4% (95% CI, 3%-6%), 11% (95% CI, 8%-15%) by age 40, 24% (95% CI, 19%-31%) by age 60 and 35% (95% CI, 25%-47%) by age 80. The overall risk of metastatic disease for non-proband/non-index carriers with PPGL was 9% (95% CI, 5-16%) per lifetime. In all affected cases (combining both proband/index and non-proband/non-index carriers with tumors), the risk of a second tumor was 24% (95% CI, 18-31%) and all cause 5-year mortality was 18% (95% CI 6-40%). CONCLUSION:Penetrance for PPGL in SDHB PV carriers increases linearly with age. Affected carriers are at risk of developing and dying from metastatic disease, or of developing second tumors. Lifelong surveillance is appropriate.