5533 Background: Significant improvements in the management of MGCOC have been achieved during the past two decades. However, data on long term risk conferred by radiation and chemotherapy is scarce. This is a long-term follow-up study of presentation, survival and second cancers. Methods: 360 female patients with histologically confirmed MGCOC, recorded in the CRN between 1953 and 2009 were identified. Patients, diagnosed before 1980 were separated from those with a diagnosis 1980+, reflecting the introduction of cis-platin based chemotherapy. Data on survival and second cancer incidence were obtained by linkage to the CRN. Cox Hazards Models and Kaplan Meier estimates were used. Results: The annual incidence doubled during the observation time. Malignant teratoma was the most common histological subtype (n = 190 [53%]), followed by dysgerminoma (n = 113 [31%]) and other non - dysgerminoma tumors (n = 57 [16%]). Over two thirds of the patients (median age 34 years [range 2-92]) had localized disease with distant disease in 23%. Before 1980 70% of 159 patients received subdiaphragmatic radiotherapy, this percentage was reduced to 24% after 1980, while chemotherapy increased from 11% to 38%. The 10 years ovarian cancer specific survival (OvCSS) (median follow-up time of 9.8 years [range: 0 - 54]) increased significantly to 93% in women treated in 1980+ compared to 62% to those with an earlier diagnosis (p <0.001) . Significant period-related improvement in OvCSS was observed independently from the extent of the disease and for all histological subtypes. Women aged >50 years had a significantly poorer OvCSS than younger ones, (HR=5.98, 95%CI [3.39 to 10.57]) adjusted for histological type and stage. A second cancer was diagnosed in 27 women, 63% of these cancers were located below the diaphragm within or close to the radiation field. Conclusions: The incidence of MGCOC is rising in Norway. We observed significant improvement of ovarian cancer specific survival after the introduction of cisplatin-based chemotherapy. The development of second cancer after treatment for MGCOC seems to be related to abdominal radiotherapy.