[1] Canc Registry Norway, Dept Screening Based Res, N-0304 Oslo, Norway
[2] Univ Copenhagen, Rigshosp, Danish Canc Soc, Inst Canc Epidemiol, DK-2100 Copenhagen, Denmark
[3] Univ Copenhagen, Rigshosp, Dept Obstet & Gynecol, DK-2100 Copenhagen, Denmark
[4] Iceland Canc Registry, Reykjavik, Iceland
[5] Univ Iceland, Dept Med, Reykjavik, Iceland
[6] Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden
[7] Merck & Co Inc, Merck Res Labs, Upper Gwynedd, PA USA