Clinical presentation of MEN 2A in index vs. non-index patients.

PURPOSE: Differences in syndromic manifestations of multiple endocrine neoplasia 2 A (MEN2A) between index and non-index patients are ill-defined. METHODS: Cross-sectional analysis of 602 REarranged during Transfection (RET) carriers (156 index and 446 non-index patients) who underwent thyroidectomy, adrenalectomy, and/or parathyroidectomy between 1985 and 2022, stratified by mutational risk. RESULTS: Index patients were 5.8-13.9 years older at thyroidectomy than non-index patients, at which point they had developed 10.6-14.4 mm larger medullary thyroid cancers. Correlations between index status and primary tumor size (ρ = 0.489-0.544) were stronger than correlations between index status and age at thyroidectomy (ρ = 0.359-0.438). For pheochromocytoma and primary hyperparathyroidism, no significant differences were noted. When stratified by time of surgery before vs. in the new millennium, age at thyroidectomy fell significantly only for non-index patients in the new millennium: from 28.6 to 21.2 years (moderate-high risk mutations; P = 0.049) and from 23.1 to 12.3 years (high-risk mutations; P < 0.001). All other inter-millennium comparisons did not reach statistical significance. CONCLUSION: These findings imply that differences between index and non-index patients impact the first syndromic manifestation without extending to subsequent syndromic manifestations. Because they exhibited similar age and tumor characteristics for the secondary and tertiary manifestations of MEN2A, screening for these syndromic components remains an integral element of MEN2A management in index and non-index patients alike. Wider use of population genomic screening may work to diminish the observed disparities between index and non-index patients going forward.