Breast cancer incidence and case fatality among 4.7 million women in relation to social and ethnic background: a population-based cohort study
Cette étude de cohorte en population suédoise (4, 7 millions de participantes) évalue l'association entre le niveau socioéconomique, l'origine ethnique et le risque de cancer du sein
INTRODUCTION:Incidence of breast cancer is increasing around the world and still it is the leading cause of cancer mortality in low- and middle-income countries. We utilized Swedish nationwide registers to study breast cancer incidence and case fatality to disentangle the effect of socioeconomic position (SEP) and immigration from the trends in native Swedes.METHODS:A nation-wide cohort of women in Sweden was followed between 1961 and 2007 and incidence rate ratio (IRR) and hazard ratio (HR) with 95% confidence intervals (CIs) were estimated using Poisson and Cox proportional regression models, respectively.RESULTS:Incidence continued to increase however it remained lower among immigrants (IRR=0.88, 95% CI=0.86 to 0.90) but not among immigrant's daughters (IRR=0.97, 95% CI=0.94 to 1.01) compared to native Swedes. Case fatality decreased over the last decades and was similar in native Swedes and immigrants. However, case fatality was significantly 14% higher if cancer was diagnosed after age 50 and 20% higher if cancer was diagnosed in the most recent years among immigrants compared with native Swedes. Women with the highest SEP had significantly 20% to 30% higher incidence but had 30% to 40% lower case fatality compared with women with lowest SEP irrespective of country of birth. Age at immigration and duration of residence significantly modified the incidence and case fatality.CONCLUSIONS:Disparities found in case fatality among immigrants by age, duration of residence, age at immigration and country of birth emphasize the importance of targeting interventions on women that are not likely to attend screening or are not likely to adhere to the therapy suggested by physicians. The lower risk of breast cancer amongst immigrant women calls for more knowledge about how the lifestyle factors in these women differ from those with high risk, so that preventative measures may be implemented.