[The accuracy of the causes of death and the estimated trend: the case of cervix uteri]. / L'accuratezza delle cause di morte e la stima dei trend: il caso della cervice uterina.

BACKGROUND: reduction in cervical cancer mortality is the ultimate goal of the screening. Quality of death certificate reports has been improved over time, but they are still inaccurate, making it difficult to assess time trends in mortality. OBJECTIVES: to evaluate the accuracy of the topographic coding of causes of death and to estimate the mortality time trend for cervical cancer through the method of incidence-based mortality (IBM) using cancer registry (CR) data. DESIGN: from the mortality registry (MR), we extracted data on deaths for cervix uteri cancer, corpus uteri cancer, and uterus cancer not otherwise specified (NOS) referred to residents in Reggio Emilia (Emilia-Romagna Region, Northern Italy) from 1997 to 2013. Deaths were checked with the CR to verify the topographical site of the primary tumour. Furthermore, by using CR data, we constructed a cohort of incident cervical cancer cases diagnosed between 1997 and 2009 with a 5-year follow-up. We calculated cause-specific IBM (excluding ovary) and IBM for all cause, crude and standardized, and annual percentage change (APC). RESULTS: out of 369 deaths for uterine cancer, 269 were reported in the RT: 32 for cervix uteri cancer, 76 for corpus uteri cancer, 161 for uterus cancer NOS. 28 of the 32 persons who died for cervical cancer were incidents for cervix uteri cancer. 63 of the 76 who died for corpus uteri cancer were incidents for corpus uteri cancer. Of the 161 who died of uterus cancer NOS, 80 were incidents for corpus uteri cancer, 45 for cervix uteri cancer, 28 for uterus cancer NOS, 5 for vagina cancer, and 3 for cancer of other non-specified organs. Applying these proportions of misclassification, we can estimate that the real number of cervical cancer deaths is 2.4 folds the number of cases reported in the MR as cervical cancer. IBM for all causes decreased significantly over the years (APC: -9.5; 95%CI -17.1;-1.1); cause-specific IBM decreases, but not significantly (APC: -5.1; 95%IC -16.1;+7.3). There is no improvement in survival (r2=0.02; p=0.6), while the incidence shows a decrease (APC: -6.6;95%CI -10.0;-3.0). CONCLUSIONS: mortality for cervical cancer is still underestimated by deaths certificates: for each reported case, there are other 1.4 cases that are reported with other less specific causes.