Type of hormone therapy and risk of misclassification at mammography screening.
OBJECTIVE
Current users of hormone therapy (HT) are known to have a lower accuracy of mammography screening than do never users. We studied whether the risk of misclassification depends on type of hormone, administration, regimen, and dose of the therapy.


METHODS
We linked data from mammography screening registers with drug prescription registers from Fyn, Denmark to identify current and never HT users among screening participants. We compared false-positive risks and interval cancer proportions between current users of different HT preparations, taking women's age, breast density, screen number, and age of comparison mammogram into account.


RESULTS
Estrogen therapy users had a significantly higher false-positive risk when the administration was by injection instead of oral (relative risk [RR], 2.37; 95% CI, 1.37-4.09). Women using sequential estrogen plus progestogen therapy had a significantly higher false-positive risk (RR, 1.94; 95% CI, 1.16-3.26) and a nonsignificantly higher interval cancer proportion (RR, 4.29; 95% CI, 0.69-26.53) when the administration of both hormones was transdermal instead of oral. Using tibolone instead of comparable hormones gave a nonsignificantly lower false-positive risk and a nonsignificantly higher interval cancer proportion.


CONCLUSIONS
Our data showed increased risks of misclassification at mammography screening among women using estrogen injections or transdermal, sequential estrogen plus progestogen. Tibolone seems to offer no advantage regarding accuracy of screening mammography.
Njor
Sisse H
SH
Institute of Public Health, University of Copenhagen, Copenhagen N, Denmark. S.Njor@pubhealth.ku.dk
Hallas
Jesper
J
Schwartz
Walter
W
Lynge
Elsebeth
E
Pedersen
Anette Tønnes
AT
D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D002277:Carcinoma / Q000000981:diagnostic imaging*; D003718:Denmark / Q000453:epidemiology; D003951:Diagnostic Errors; D055088:Early Detection of Cancer; D005260:Female; D020249:Hormone Replacement Therapy / Q000009:adverse effects*; D006801:Humans; D008327:Mammography / Q000706:statistics & numerical data*; D008403:Mass Screening; D008875:Middle Aged; D012306:Risk; D016896:Treatment Outcome