Spatial analysis of breast and cervical cancer incidence in small geographical areas in Cuba, 1999-2003.

ABSTRACT

According to the data from the National Cancer Registry, breast and cervical cancer are the two most common nonskin cancers in Cuban woman. This study was addressed to describe the geographical variation of their incidence at small area level over the period 1999-2003. For each municipality, standardized incidence ratios were calculated and smoothed using a Poisson-Gamma, Poisson-Lognormal and a Conditional Autoregressive (CAR) model. The covariate 'urbanization level' was included in the Poisson-Lognormal and CAR models. The posterior probability of each municipality's relative risk (RR) exceeding unity was computed. Clusters were confirmed using the spatial scan statistic of Kulldorff. The CAR model provided the best fit for the geographical distribution of breast and cervical cancer in Cuba. For breast cancer, a high-risk region was identified in municipalities of Ciudad de La Habana province (CAR-smoothed RR between 1.21 and 1.26). Cervical cancer exhibited two areas with excess risk in the east and extreme west of the island (CAR-smoothed RR range 1.2-2.01 both areas together). Clusters were confirmed only for cervical cancer (P = 0.001 for the most likely cluster and P = 0.003 for a secondary cluster). In conclusion, the study supports the hypothesis of a spatial variation in risk at small area level essentially for cervical cancer and also for breast cancer that probably reflects the territorial distribution of life style and socioeconomic factors. This is the first attempt to introduce this methodology in the framework of the National Cancer Registry of Cuba and we expect to extend its use to forthcoming analyses.