The findings in this examination of the cancer registry data from Brooklyn, NY, Guyana and Trinidad & Tobago give a fair representation of prostate cancer in males of African ancestry. There were approximately 62% black males in this study population and for the first time we report and compare survival rates for prostate cancer cases from two population cancer registries in the Caribbean and a hospital-based cancer registry in Brooklyn, USA. This is the first and largest study of prostate cancer survival using combined cancer registry data from the Caribbean and the United States. This study has allowed us to compare the within-group differences in survival among Black men from two distinct geographic regions (US and the Caribbean).
The low survival rate has been clearly illustrated in Caribbean born prostate cancer cases in this study population. For those cases born in the United States, their diagnosis age was younger than their Caribbean registry counterparts. The mean age of diagnosis for Brooklyn males was 66 years. A significant proportion of Brooklyn cases were black (87%); age at diagnosis is consistent with previous reports, showing that the median age of diagnosis for black males in the United States is 65 years (11
). Consistent with other studies in Caribbean populations(12
), this study shows that Caribbean men from Trinidad & Tobago and Guyana are diagnosed at an older age compared to men in Brooklyn. This suggests a possible limited access to healthcare and/or low screening prevalence. The younger age at prostate cancer diagnosis for Brooklyn, NY compared to the Caribbean countries examined was possibly due to education, and early detection methods. Low education and literacy level on cancer screening in older Caribbean men has been shown to be related to under-use of services available (15
). On the island of Tobago, a longitudinal screening study on serum prostate-specific antigen (PSA) in local volunteers reported a high amount of screening-detected prevalence of prostate cancer (5
). However this may not entirely explain the differences between Brooklyn and the Caribbean. Similar to Brooklyn, the highest proportions of Caribbean patients were diagnosed with stage I-III disease. However, the distribution of stage at diagnosis needs to be interpreted with caution since a large proportion of cases were un staged for the Caribbean registry sites.
Ad hoc studies are needed to assess the relationship between age at diagnosis and stage in Caribbean-born men compared to US-born men.
Our results show that males diagnosed in the Caribbean tend to have significantly worse survival outcomes compared to males diagnosed in Brooklyn. However survival rates for African-American men and Caribbean-born Black men who were diagnosed in the US were similar. It is estimated by the World Health Organization that 70% of prostate cancer deaths occur in low to middle income countries where persistent disparities hinder detection and treatment (16
). It is possible that the similar survival rates between African-American and Caribbean-born Black males in the US are likely due to the easier access to early detection and treatment compared to those men who were diagnosed in the Caribbean. Recently, Meliler et al. evaluated prostate cancer survival disparities according to different geographic scales in the state of Michigan, USA(17
). The study reported that the observed survival disparity between Blacks and Whites for the state was diminished when the analysis was restricted to smaller geographic units such as community-defined neighborhoods and state House legislative districts. These findings suggest that individual/genetic risk factors may not necessarily explain the reduction in survival disparity between Blacks and White according to geographic scale. Widely recognized risk factors for prostate cancer include aging, geographic origin, in addition to a family history of prostate cancer (18
). A commonly stated hypothesis is that genetic factors contribute to the high risk for prostate cancer among populations of African origin (1
)and other studies suggest that there may be an important influence of environmental/lifestyle factors acting on prostate cancer risk as illustrated by the variability in rates between the populations of African descent in different geographic locations (4
). We did not observe a significant difference in risk of death for Caribbean-born Black men in Brooklyn, when compared to US-born Black men in Brooklyn; in contrast there was a twelve-fold and four-fold increased risk of death for Caribbean-born men from Guyana and Trinidad & Tobago respectively. The excessively high Hazard ratio with a wide confidence interval for Caribbean-born Guyanese males is an imprecise estimate due the small sample of Guyanese men. Nevertheless, the overall findings support the inferences that environment/lifestyle factors may play a more important role in prostate cancer survival for Caribbean-born Black men. Therefore further studies that compare and contrast sociodemographic and environmental risk factors in prostate cancer among US and Caribbean populations are necessary in order to help close the gap in survival disparities within the black population.
This study’s limitations arose primarily from incomplete data. Many cases were not classified into ethnic groups, nor were their grade and stage at diagnosis noted. These are important variables that could shed light into whether there are significant differences in the stage and grade of diagnosis in different locations, and thus reveal more about the disease that afflicts so many men. It should be taken into account that some of the data used in this analysis was incomplete with respect to clinical characteristics and could thus influence the interpretation of some results. A high proportion of cases were classified as carcinoma and the specific histologic type was not defined, therefore we were not able to evaluate whether more aggressive histologic types among Caribbean males might contribute to the poor survival rates in this population.
Although environmental/lifestyle factors may be very important predictors of survival for Black Caribbean-born men, genetic risk factors cannot be ruled out. Future association studies involving genetic factors in recently immigrated Caribbean and African-American prostate cancer patients are still necessary. This will also help to provide a better understanding of the reasons for such large differences in the survival rates between the two geographic regions. A vital question to be answered in future studies is whether the differences we observed still exits after adjusting for access to care and screening.