['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.', 'We described a retrospective cohort study with a median follow-up of 8 years (range 1-35 years).', '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 were overall and disease-specific survival and life expectancy expressed as survival adjusted for baseline mortality rate in the general population.', '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.'] Does determinants of life expectancy in medullary thyroid cancer : age matter?