Cohort study examining tamoxifen adherence and its relationship to mortality in women with breast cancer

C. McCowan, J. Shearer, P.T. Donnan, J.A. Dewar, M. Crilly, A.M. Thompson, T.P. Fahey

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Increasing duration of tamoxifen therapy improves survival in women with breast cancer but the impact of adherence to tamoxifen on mortality is unclear. This study investigated whether women prescribed tamoxifen after surgery for breast cancer adhered to their prescription and whether adherence influenced survival. A retrospective cohort study of all women with incident breast cancer in the Tayside region of Scotland between 1993 and 2002 was linked to encashed prescription records to calculate adherence to tamoxifen. Survival analysis was used to determine the effect of adherence on all-cause mortality. In all 2080 patients formed the study cohort with 1633 (79 prescribed tamoxifen. The median duration of use was 2.42 years (IQR=1.04-4.89 years). Longer duration was associated with better survival but this varied over time. The hazard ratio for mortality in relation to duration at 2.4 years was 0.85, 95% CI=0.83-0.87. Median adherence to tamoxifen was 93% (interquartile range=84-100. Adherence 60;80% was associated with poorer survival, hazard ratio 1.10, 95% CI=1.001-1.21. Persistence with tamoxifen was modest with only 49% continuing therapy for 5 years of those followed up for 5 years or more. Increased duration of tamoxifen reduces the risk of death, although one in two women do not complete the recommended 5-year course of treatment. A significant proportion of women have low adherence to tamoxifen and are at increased risk of death.
Original languageUndefined/Unknown
Pages (from-to)1763-1768
Number of pages6
JournalBritish Journal of Cancer
Issue number11
Publication statusPublished - 1 Dec 2008

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