Trends in the Incidence, Organization of Care, and Surgical Treatment of Medullary Thyroid Cancer: A Population-Based Study.

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Background: Medullary thyroid cancer (MTC) is a rare cancer with variable disease course. To enable optimal care, centralization and consensus guidelines are essential. This study describes trends in the incidence, organization of care, surgical treatment, and outcomes of MTC over 30 years in the Netherlands. Methods: All patients with a histological MTC diagnosis between 1989 and 2018 were identified from the Netherlands Cancer Registry and linked to the Dutch Pathology register (PALGA). Incidence rates, relative to the Dutch population, were assessed throughout time. Clinicopathological parameters and extent of lymph node (LN) surgery were extracted from PALGA pathology reports. Period A (1989-1998), period B (1999-2008), and period C (2009-2018) were compared. Results: Throughout 30 years, the population-adjusted incidence remained stable with 0.17 ± 0.04 diagnoses per 100,000 people per year (p = 0.247). Of all 795 patients, 54% were female and 63% were treated in an academic hospital, at a median age of 48 years (interquartile range [IQR] 34-61). Age at diagnosis increased over time from 42 years (IQR 25-61) in period A to 52 years (IQR 42-63) in period C (p < 0.001). The proportion of treatments occurring in an academic hospital increased from 41% of patients in period A to 58% and 86% in period B and C, respectively (both p < 0.001). At primary treatment, a LN dissection was performed in 582 (73%) patients. Of these patients, 88%, 36%, and 20% underwent a central neck dissection (CND), unilateral neck dissection, and bilateral neck dissection, respectively. CND was performed more frequently in period C (93%) than in period A (77%) or B (87%) (p = 0.009, p = 0.027, respectively). Overall survival improved from period A (55%) to C (88%) and B (65%) to C (p = 0.022, p = 0.007, respectively). Locoregional recurrence rates remained stable. Conclusions: This study shows a stable incidence and improved survival of MTC in the Dutch population over the last three decades. In addition, these data indicate a transition of treatment to academic hospitals, likely due to centralization, and a higher rate of CNDs, following the introduction of recommendation guidelines.