Cervical carcinoma and reproductive factors: Collaborative reanalysis of individual data on 16,563 women with cervical carcinoma and 33,542 women without cervical carcinoma from 25 epidemiological studies

Authors

  • International Collaboration of Epidemiological Studies of Cervical Cancer

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    • International Agency for Research on Cancer, 150 cours Albert Thomas, 69372 Lyon cedex 08, France
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    • Analysis and writing committee: P Appleby, V Beral, A Berrington de González, D Colin, S Franceschi, J Green, C La Vecchia, J Peto, M Plummer, G Randi, S Sweetland.

      Steering committee: FX Bosch, R Herrero, A Hildesheim, C La Vecchia (chairman), D Skegg, D Thomas.

      Collaborators: Cancer Institute (WIA), Chennai, India: T Rajkumar; Cancer Research UK Epidemiology Group, Wolfson Institute of Preventive Medicine, London, UK: J Cuzick; Cancer Research UK Epidemiology Unit, Oxford, UK: P Appleby, R Barnabas, V Beral, A Berrington de González, D Bull, K Canfell, B Crossley, J Green, G Reeves, S Sweetland; Danish Cancer Society, Copenhagen, Denmark: S Kjaer; Unit of Health Care Epidemiology, Oxford, UK: R Painter, M Vessey; Fred Hutchinson Cancer Research Center, Seattle, Washington, USA: J Daling, M Madeleine, R Ray, D Thomas; Guanacaste Epidemiological Project, San José, Costa Rica: R Herrero; Department of Medical Epidemiology and Biostatistics, Karolinska Institut, Stockholm, Sweden: N Ylitalo; Epidemiology and Cancer Registration Unit, IDIBELL, Institut Català d'Oncologia, Barcelona, Spain: FX Bosch, S de Sanjosé, X Castellsagué, V Moreno; Institut Nacional de Santé Publique, Algiers, Algeria: D Hammouda; Istituto di Ricerche Farmacologiche ‘Mario Negri’, Milan, Italy: E Negri, G Randi; Instituto Especializado de Enfermedades Neoplásicas ‘Dr Eduardo Cáceres Graziani’, Lima, Peru: M Alvarez, O Galdos, C Santos, C Velarde; International Agency for Research on Cancer, Lyon, France: D Colin, S Franceschi, N Muñoz, M Plummer; London School of Hygiene and Tropical Medicine, London and Institute of Cancer Research, Sutton, UK: J Peto; Lund University, Mälmo, Sweden: J Dillner, I Silins; Ministere de la Santé Publique et des Affaires Sociales, Bamako, Mali: S Bayo; Ministry of Health, Rabat, Morocco: N Chaouki; Ministry of Health, Asunción, Paraguay: PA Rolón; National Cancer Institute, NIH, Bethesda, Maryland, USA: L Brinton, A Hildesheim, J Lacey Jr, M Schiffman; Cancer Epidemiology Research Group, National Health Laboratory Service, Johannesburg, South Africa: L Stein, MI Urban; Royal College of General Practitioners Oral Contraception Study, UK: P Hannaford; Prince of Songkla University, Songkla, Thailand: SB Chichareon; The Cancer Council New South Wales, Sydney, Australia: F Sitas; Universidade de São Paulo, São Paulo, Brazil: J Eluf-Neto; University of Milan, Milan, Italy: C La Vecchia; University of Otago, Dunedin, New Zealand: D Skegg; University of Southern California, Los Angeles, California, USA: R Peters, M Pike, G Ursin; University of the Philippines, Manila, The Philippines: C Ngelangel; University of Tromsø, Tromsø, Norway: IT Gram; World Health Organisation, Geneva, Switzerland: T Farley, O Meirik.

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Abstract

The International Collaboration of Epidemiological Studies of Cervical Cancer has combined individual data on 11,161 women with invasive carcinoma, 5,402 women with cervical intraepithelial neoplasia (CIN)3/carcinoma in situ and 33,542 women without cervical carcinoma from 25 epidemiological studies. Relative risks (RRs) and 95% confidence intervals (CIs) of cervical carcinoma in relation to number of full-term pregnancies, and age at first full-term pregnancy, were calculated conditioning by study, age, lifetime number of sexual partners and age at first sexual intercourse. Number of full-term pregnancies was associated with a risk of invasive cervical carcinoma. After controlling for age at first full-term pregnancy, the RR for invasive cervical carcinoma among parous women was 1.76 (95% CI: 1.53–2.02) for ≥≥7 full-term pregnancies compared with 1–2. For CIN3/carcinoma in situ, no significant trend was found with increasing number of births after controlling for age at first full-term pregnancy among parous women. Early age at first full-term pregnancy was also associated with risk of both invasive cervical carcinoma and CIN3/carcinoma in situ. After controlling for number of full-term pregnancies, the RR for first full-term pregnancy at age <17 years compared with ≥≥25 years was 1.77 (95% CI: 1.42–2.23) for invasive cervical carcinoma, and 1.78 (95% CI: 1.26–2.51) for CIN3/carcinoma in situ. Results were similar in analyses restricted to high-risk human papilloma virus (HPV)-positive cases and controls. No relationship was found between cervical HPV positivity and number of full-term pregnancies, or age at first full-term pregnancy among controls. Differences in reproductive habits may have contributed to differences in cervical cancer incidence between developed and developing countries. © 2006 Wiley-Liss, Inc.

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