Trends in treatment and long-term survival of thyroid cancer in southeastern Netherlands, 1960-1992

Thyroid cancer (TC), comprising less than 1% of all cancers in the Netherlands, has a good prognosis in general. Controversy still remains on the extent of surgical treatment and the indication for additional Iodine-131 (131I) therapy in the management of differentiated TC. The aim of this study was to describe (changes in) the treatment of TC and to determine independent prognostic factors for crude and relative survival of differentiated TC diagnosed in general hospitals. This population-based, retrospective study was based on data from the Eindhoven Cancer Registry, Comprehensive Cancer Centre South (I.K.Z.), Eindhoven, the Netherlands. Data were collected on all 343 TC patients diagnosed from 1 January 1960 to 31 December 1992. All available information on treatment (initial and additional) and survival (on 1 April 1994) were recorded. Initial surgical treatment was defined as limited or extended. Multivariate analysis of crude and relative survival to determine prognostic factors for differentiated TC was performed. Mean follow-up was 7.6 years. The proportion of patients with differentiated TC increased from 60% in 1960-1972 to 84% in 1985-1992. TC patients were treated in all hospitals in the region, approximately 2-4/year. Ninety per cent of all TC patients initially underwent surgical treatment; the extended procedures increasing from 27% in 1960-1974 to 61% in 1985-1992. 131I was also administered increasingly (from 18-44%) to patients with differentiated TC. The relative 5, 10 and 20 year survival rates for all TC were 80, 75 and 75%, respectively. In the first 5 years after diagnosis the crude death ratio was higher with the rise of age and for the follicular type and after 5 years for males and advanced disease. After inclusion of surgical treatment into the model, the estimates of the other death ratios did not change. Patients treated with 131I did better only during the first 5 years. Although the prognosis for TC patients treated in general hospitals in Southeastern Netherlands was similar to that found for patients treated in referral centres, concentration of treatment should be considered.