{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T07:21:35Z","timestamp":1790061695753,"version":"4.0.1"},"reference-count":30,"publisher":"Wiley","issue":"6","license":[{"start":{"date-parts":[[2003,4,9]],"date-time":"2003-04-09T00:00:00Z","timestamp":1049846400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Intl Journal of Cancer"],"published-print":{"date-parts":[[2003,7,20]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>The aim of our study was to examine the risk of breast cancer according to specific types of estrogens and progestagens in oral contraceptives (OCs) based on the prospective Norwegian Women and Cancer study (NOWAC). Between 1991\u201397 women aged 30\u201370 years were drawn at random from the central person register and mailed an invitation and a questionnaire. Women (102,443) were enrolled with follow\u2010up information collected throughout 1999 by linkage with national registries of cancer, mortality and emigration based on the unique national identification number. Among the 96,362 women included in the present analysis 851 invasive breast cancer were diagnosed. The adjusted risk of breast cancer increased with 25% for ever use of OCs and the risk increased with increasing duration of use (test for trend: <jats:italic>p<\/jats:italic> = 0.007). No association between time since last use and breast cancer risk was found after stratification on duration of use. Positive trend was still found for total duration of use among women 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\u2010significant, although we observed a significant increased risk with increasing milligram\u2010months of estrogen exposure (<jats:italic>p<\/jats:italic> = 0.002). In conclusion, the increased risk of breast cancer related with OC formulations could be due mostly to estrogen component. \u00a9 2003 Wiley\u2010Liss, Inc.<\/jats:p>","DOI":"10.1002\/ijc.11167","type":"journal-article","created":{"date-parts":[[2003,5,20]],"date-time":"2003-05-20T11:34:57Z","timestamp":1053430497000},"page":"844-850","source":"Crossref","is-referenced-by-count":53,"title":["Breast cancer and specific types of oral contraceptives: A large Norwegian cohort study"],"prefix":"10.1002","volume":"105","author":[{"given":"Vanessa","family":"Dumeaux","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Elin","family":"Alsaker","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eiliv","family":"Lund","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2003,5,15]]},"reference":[{"key":"e_1_2_6_2_2","doi-asserted-by":"crossref","first-page":"1S","DOI":"10.1016\/S0010-7824(15)30002-0","article-title":"Breast cancer and hormonal contraceptives: further results","volume":"54","author":"Collaborative Group on Hormonal Factors in Breast Cancer","year":"1996","journal-title":"Contraception"},{"key":"e_1_2_6_3_2","doi-asserted-by":"publisher","DOI":"10.1038\/bjc.1983.74"},{"key":"e_1_2_6_4_2","doi-asserted-by":"publisher","DOI":"10.1056\/NEJM198608143150701"},{"key":"e_1_2_6_5_2","doi-asserted-by":"publisher","DOI":"10.1093\/ije\/20.1.32"},{"key":"e_1_2_6_6_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(94)92826-6"},{"key":"e_1_2_6_7_2","doi-asserted-by":"publisher","DOI":"10.1093\/oxfordjournals.aje.a008654"},{"key":"e_1_2_6_8_2","doi-asserted-by":"publisher","DOI":"10.1038\/bjc.1987.261"},{"key":"e_1_2_6_9_2","doi-asserted-by":"publisher","DOI":"10.1038\/bjc.1992.20"},{"key":"e_1_2_6_10_2","first-page":"973","article-title":"Oral contraceptives and cancer risk in young women","volume":"1","author":"UK National Case\u2010Control Study Group","year":"1989","journal-title":"Lancet"},{"key":"e_1_2_6_11_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(83)90450-6"},{"key":"e_1_2_6_12_2","doi-asserted-by":"publisher","DOI":"10.1016\/0959-8049(92)90481-G"},{"key":"e_1_2_6_13_2","doi-asserted-by":"publisher","DOI":"10.1093\/jnci\/86.7.505"},{"key":"e_1_2_6_14_2","first-page":"1","article-title":"The person\u2010number systems of Sweden, Norway, Denmark, and Israel","volume":"2","author":"Lunde AS","year":"1980","journal-title":"Vital Health Stat 2"},{"key":"e_1_2_6_15_2","doi-asserted-by":"publisher","DOI":"10.1177\/14034948980260020401"},{"key":"e_1_2_6_16_2","first-page":"11","volume-title":"Incidence of cancer in Norway, 1978","author":"Lund E","year":"1981"},{"key":"e_1_2_6_17_2","doi-asserted-by":"crossref","first-page":"1582","DOI":"10.1016\/S0140-6736(95)91927-9","article-title":"World Health Organization Collaborative Study of Cardiovascular Disease and Steroid Hormone Contraception. 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