The aim of our study was to examine the risk of @entity0 according to specific types of @entity172 and progestagens in oral contraceptives (OCs) based on the prospective Norwegian @entity1 and @entity5 study (NOWAC). Between 1991-97 @entity1 aged 30-70 years were drawn at random from the central @entity1 register and mailed an invitation and a questionnaire. @entity1 (102,443) were enrolled with follow-up information collected throughout 1999 by linkage with national registries of @entity5 , mortality and emigration based on the unique national identification number. Among the 96,362 @entity1 included in the present analysis 851 @entity0 were diagnosed. The adjusted risk of @entity0 increased with 25% for ever use of OCs and the risk increased with increasing duration of use (test for trend: p = 0.007). No association between time since last use and @entity0 risk was found after stratification on duration of use. Positive trend was still found for total duration of use among @entity1 who used OCs more than 5 years ago. Second generation of OCs had an increased risk with increasing duration of use. Classifying progestagens according to chemical groups, the relative risk increased significantly with increasing cumulative dose of levonorgestrel progestagen. It was difficult to conclude for the other groups due to lack of power. In a multivariate analysis the cumulative dose for all progestagen groups were non-significant, although we observed a significant increased risk with increasing milligram-months of @entity172 exposure (p = 0.002). In conclusion, the increased risk of @entity0 related with OC formulations could be due mostly to @entity172 component.

XXXX and specific types of oral contraceptives: a large Norwegian cohort study.

@entity172 :: ('MESH:D004967', 'Chemical') :: ['estrogen', 'estrogens'] @entity1 :: ('9606', 'Species') :: ['women', 'Women', 'person'] @entity5 :: ('MESH:D009369', 'Disease') :: ['cancer', 'Cancer'] @entity0 :: ('MESH:D001943', 'Disease') :: ['breast cancer', 'invasive breast cancer']
@entity0 :: (MESH:D001943,Disease) :: ['Breast cancer']
