Breast cancer incidence after hormonal infertility treatment in Sweden: a cohort study.
OBJECTIVE
To assess the impact of infertility treatment with causes of infertility on incidence of breast cancer.


METHODS
Historical prospective cohort study of 1135 women attending major university clinics for treatment of infertility in Sweden, 1961-1976. Women were classified as users of clomiphene citrate or gonadotropins, or a combination of both therapies. Standardized incidence ratios were calculated to estimate relative risk of breast cancer.


RESULTS
We observed 54 cases of breast cancer during 1961-2004, which did not significantly exceed those expected. Users of high-dose clomiphene citrate had an almost 2-fold increased risk (standardized incidence ratio, 1.90; 95% confidence interval, 1.08-3.35). This association was more pronounced among women referred for nonovulatory factors, with 3-fold increased risk (standardized incidence ratio, 3.00; 95% confidence interval, 1.35-6.67).


CONCLUSIONS
No overall increased risk for breast cancer was shown with infertility treatment. Women with nonovulatory causes treated with high-dose clomiphene citrate therapy may have an elevated risk for breast cancer.
Orgéas
Chantal C
CC
Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden. Chantal.Orgeas@ki.se
Sanner
Karin
K
Hall
Per
P
Conner
Peter
P
Holte
Jan
J
Nilsson
Staffan J
SJ
Sundfeldt
Karin
K
Persson
Ingemar
I
Chia
Kee Seng
KS
Wedren
Sara
S
Dickman
Paul W
PW
Czene
Kamila
K
D000328:Adult; D001943:Breast Neoplasms / Q000139:chemically induced* / Q000453:epidemiology; D006063:Chorionic Gonadotropin / Q000009:adverse effects* / Q000627:therapeutic use; D002996:Clomiphene / Q000009:adverse effects* / Q000627:therapeutic use; D015331:Cohort Studies; D005260:Female; D005300:Fertility Agents, Female / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D015994:Incidence; D007247:Infertility, Female / Q000188:drug therapy*; D011446:Prospective Studies; D013548:Sweden / Q000453:epidemiology
D006063:Chorionic Gonadotropin; D005300:Fertility Agents, Female; D002996:Clomiphene