The intrauterine origin of male breast cancer: a birth order study in Denmark.
First pregnancies are known to have higher oestrogen levels than later ones and first-born women are at increased breast cancer risk compared with later-born women. We hypothesized that a birth order effect might be even more evident in male breast cancer patients, in whom oestrogens in adult life are generally low. In a population-based study in Denmark involving 77 male breast cancer patients and 288 population controls, first-born men compared with later-born men had a relative risk of 1.71 for the disease (95% confidence interval (CI) 1.00-2.92). This result is in line with that seen in female breast cancer cases and indicates that male breast cancer may have roots in the intrauterine life, oestrogens being a likely mediator.
Sørensen
H T
HT
Department of Clinical Epidemiology, Aarhus University Hospital, Ole Worms Allé 150, 8000 Aarhus C, Denmark. hts@dce.au.dk
Olsen
M L
ML
Mellemkjaer
L
L
Lagiou
P
P
Olsen
J H
JH
Olsen
J
J
D001722:Birth Order; D018567:Breast Neoplasms, Male / Q000453:epidemiology / Q000209:etiology*; D016022:Case-Control Studies; D003718:Denmark / Q000453:epidemiology; D004967:Estrogens / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012307:Risk Factors
D004967:Estrogens