Hormonal therapy for oestrogen receptor-negative breast cancer is associated with higher disease-specific mortality.
BACKGROUND
Tamoxifen has a remarkable impact on the outcome of oestrogen receptor (ER)-positive breast cancer. Without proven benefits, tamoxifen is occasionally prescribed for women with ER-negative disease. This population-based study aims to estimate the impact of tamoxifen on the outcome of ER-negative disease.


METHODS
We identified all women (n = 528) diagnosed with ER-negative invasive breast cancer between 1995 and 2005. With Cox regression analysis, we calculated breast cancer mortality risks of patients treated with tamoxifen compared with those treated without tamoxifen. We adjusted these risks for the individual probabilities (propensity scores) of having received tamoxifen.


RESULTS
Sixty-nine patients (13%) with ER-negative disease were treated with tamoxifen. Five-year disease-specific survival for women treated with versus without tamoxifen were 62% [95% confidence interval (CI) 48% to 76%] and 79% (95% CI 75% to 83%), respectively (P(Log-rank) < 0.001). For ER-negative patients, risk of death from breast cancer was significantly increased in those treated with tamoxifen compared with patients treated without tamoxifen (adjusted hazard ratio = 1.7, 95% CI 1.1-2.9, P = 0.031).


CONCLUSIONS
Our results show that patients with ER-negative breast cancer treated with tamoxifen have an increased risk of death from their disease. Tamoxifen use should be avoided for these patients.
Merglen
A
A
Geneva Cancer Registry, Institute of Social and Preventive Medicine, University of Geneva, Geneva, Switzerland.
Verkooijen
H M
HM
Fioretta
G
G
Neyroud-Caspar
I
I
Vinh-Hung
V
V
Vlastos
G
G
Chappuis
P O
PO
Castiglione
M
M
Rapiti
E
E
Bouchardy
C
C
D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000009:adverse effects*; D001943:Breast Neoplasms / Q000737:chemistry / Q000188:drug therapy* / Q000401:mortality* / Q000473:pathology; D005260:Female; D019538:Health Care Surveys; D006801:Humans; D053208:Kaplan-Meier Estimate; D008875:Middle Aged; D018579:Patient Selection; D016016:Proportional Hazards Models; D011960:Receptors, Estrogen / Q000032:analysis*; D011980:Receptors, Progesterone / Q000032:analysis; D012042:Registries; D018570:Risk Assessment; D013557:Switzerland / Q000453:epidemiology; D013629:Tamoxifen / Q000009:adverse effects*; D013997:Time Factors; D016896:Treatment Outcome
D018931:Antineoplastic Agents, Hormonal; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D013629:Tamoxifen