Menopause hormone replacement therapy and cancer risk: an Italian record linkage investigation.
BACKGROUND
The effects of persistence with hormone replacement therapy (HRT) on the risk of hospitalization for cancer and of the route of HRT administration on the risk of breast and colorectal cancer were explored in a large cohort study.


METHODS
The 73 505 women residing in Lombardia (Italy), aged 45-75 years, who received at least one HRT prescription during 1998-2000 were followed until 2005. Among these, 3687 experienced cancer hospitalization. Proportional hazards model was fitted to estimate the association between cumulative HRT persistence and cancer risk.


RESULTS
Compared with women who took HRT for <6 months, those exposed for >2 years showed hazard ratios (HR) of 0.78 (95% confidence interval 0.68-0.92) for colorectal cancer and 1.34 (1.13-1.58) for breast cancer. HR for breast cancer associated with long-term use of transdermal and oral HRT were, respectively, 1.27 (1.07-1.51) and 2.14 (1.43-3.21).


CONCLUSIONS
Evidence that long-term use of HRT is associated with increased risk of breast cancer and decreased risk of colorectal cancer is supplied from this study from a southern European population. Our findings indicate that transdermal therapy might have lower effect than oral therapy in increasing breast cancer risk.
Corrao
G
G
Department of Statistics; Unit of Epidemiology and Biostatistics, University of Milan-Bicocca, Italy. giovanni.corrao@unimib.it
Zambon
A
A
Conti
V
V
Nicotra
F
F
La Vecchia
C
C
Fornari
C
C
Cesana
G
G
Contiero
P
P
Tagliabue
G
G
Nappi
R E
RE
Merlino
L
L
D000279:Administration, Cutaneous; D000284:Administration, Oral; D000368:Aged; D001943:Breast Neoplasms / Q000139:chemically induced / Q000453:epidemiology*; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000139:chemically induced / Q000453:epidemiology*; D015986:Confounding Factors, Epidemiologic; D004338:Drug Combinations; D015914:Estrogen Replacement Therapy / Q000009:adverse effects / Q000706:statistics & numerical data; D004967:Estrogens / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D020249:Hormone Replacement Therapy / Q000009:adverse effects* / Q000706:statistics & numerical data; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008498:Medical Record Linkage; D008593:Menopause; D008875:Middle Aged; D009369:Neoplasms / Q000139:chemically induced / Q000453:epidemiology; D011372:Progestins / Q000008:administration & dosage / Q000009:adverse effects*; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012306:Risk