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

Abstract

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 ¼ 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 ¼ 0.83 -0.87. Median adherence to tamoxifen was 93% (interquartile range ¼ 84 -100%). Adherence o80% was associated with poorer survival, hazard ratio 1.10, 95% CI ¼ 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.

Adherence to Recommended Treatments for Early Invasive Breast Cancer: Decisions of Women Attending Surgeons in the Breast Cancer Audit of Australia and New Zealand

“…Non-adherence to treatment recommendations have been shown to correlate with lower cancer survivals in previous studies cancers (Li et al, 2000;Herbert-Croteau et al, 2004;McCowan et al, 2008;Wockel et al, 2010 a, b ; Hershman et al, 2011). While the statistical power available to demonstrate similar associations in the present study was very low due to small numbers, point estimates were suggestive of higher case fatalities when treatments were declined.…”

“…Adherence to recommended treatments has been linked to higher disease-free and overall survival for breast and other cancers (Li et al, 2000;Herbert-Croteau et al, 2004;McCowan et al, 2008;Wockel et al, 2010a,b;Hershman et al, 2011). Non-adherence can be a result of many clinical factors including treatment compromises to accommodate patient frailty or co-morbidity, clinician preference, poor service access or high user cost Lebeau et al, 2011).…”

Predicting Adherence to Tamoxifen for Breast Cancer Adjuvant Therapy and Prevention

“…Previous reports have shown that approximately 1 in 5 adjuvant tamoxifen users fail to achieve an optimal adherence threshold of 80% or greater during the first year of treatment, and there is a 7% to 10% discontinuation rate per year (12,14,15). By year 4 or 5 of treatment, the full adherence rate drops to 50% (14,16).…”

“…By year 4 or 5 of treatment, the full adherence rate drops to 50% (14,16). Similarly, nonpersistence with adjuvant tamoxifen is about 20% to 30% at year 1 or 2 (15,17,18) and climbs to as high as 49% before the completion of 5 years (15,16,19). Available data on the association between adherence to adjuvant tamoxifen therapy and breast cancer outcomes have suggested that poor tamoxifen adherence contributes to therapeutic failure with an increased risk for poor outcomes.…”

Compliance with adjuvant capecitabine in patients with stage II and III colon cancer: comparison of administrative versus medical record data

“…The majority of studies on medication compliance in oncology have focused on oral hormonal therapies in breast cancer 5, 6, 11, 12, 13 even though oral drugs are also frequently used in other cancers 14, 15, 16, 17. In colon cancer, the oral 5‐fluorouracil prodrug known as capecitabine is a commonly prescribed component in a large number of systemic therapy regimens 18, 19, but it has received relatively little focus to date 20, 21, 22, 23.…”