Determinants of life expectancy in medullary thyroid cancer: age does not matter

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Abstract
Objective In medullary thyroid cancer (MTC) age is considered an important prognostic factor but survival has never been properly adjusted for baseline mortality in the general population. We aimed to identify prognostic factors by analysing patients with MTC regarding life expectancy. Design We described a retrospective cohort study with a median follow-up of 8 years (range 1–35 years). Patients We included 120 consecutive patients of whom 66 (55%) had sporadic MTC. Male/female ratio was 1 : 1; median age was 45 years (range 3–83 years). Measurements Measurements were overall and disease-specific survival and life expectancy expressed as survival adjusted for baseline mortality rate in the general population. Results Overall and disease-specific 10-year survival was 65% and 73%, respectively. After 10 years, 29% of patients were biochemically and 63% clinically cured. Median overall life expectancy was 0·58 (95%CI 0·37–0·80). Detectable recurrence occurred in 60 patients after a median of 36 months (range 5–518 months). On multivariate regression analysis only stage of disease and extrathyroidal extension predicted recurrence-free life expectancy. Extrathyroidal extension was the only independent predictor of overall life expectancy. Persistent biochemical MTC did not independently affect life expectancy but calcitonin doubling time of less than one year indicated worse prognosis. Patients without detectable recurrences after initial treatment had a life expectancy similar to the general population. Conclusions In MTC patients, extrathyroidal extension and stage at diagnosis are the only independent predictors of (recurrence-free) life expectancy. Patients diagnosed in an early stage of disease and patients without detectable recurrence have favourable life expectancy independently of biochemical cure.