During work with big clinical studies in Norway in the 1990s, clinical data on almost all patients under 65 years diagnosed with multiple myeloma in particular periods have been registered. We have registered similar data for patients under 65 years registered with multiple myeloma in the Norwegian Cancer Registry, and the diagnosis has been re-evaluated for all patients. The study gives details of the completeness and correctness of the Myelomatosis diagnosis in the Norwegian Cancer Registry. These data are compared to registrations from the 1970s, that found a completeness of around 80%.
The same data material from the early 1990s indicated significant differences in survival between multiple myeloma patients in Norway, Sweden and Denmark. One of the hypotheses for the difference was a selection effect, that the patient group included in the study was different from the rest of the population with multiple myeloma, and that this selection effect was different in the three countries.No clear significant differences are found in a comparison of prognostic factors and survival between the Norwegian patients included in the study and the Norwegians found in the Norwegian Cancer Registry who could have been included but were not.