Time dependent effects of adjuvant tamoxifen therapy on cerebrovascular disease: results from a randomised trial

BACKGROUND: Tamoxifen has been associated with an increased risk of stroke. There is, however, little information on the effect in the post-treatment period. Using data from the Swedish Breast Cancer Group adjuvant trial of 5 vs 2 years of tamoxifen treatment, we now report both short-term and long-term effects on morbidity as well as mortality because of cerebrovascular disease. METHODS: Data from the Swedish National Hospital Discharge Registry combined with information from the Swedish Cause of Death Registry was used to define events of disease. Hazard ratios (HRs) were estimated using Cox regression. RESULTS: Comparing patients randomised to 5 years of tamoxifen with patients randomised to 2 years of tamoxifen, the incidence of cerebrovascular diseases was increased (HR 1.70, 95% CI 1.05–2.75) during the active treatment phase and reduced after the active treatment period (HR 0.78, 95% CI 0.63–0.96), and the difference in HR between the two time-periods was significant (P=0.0033). The mortality from cerebrovascular diseases was increased during the treatment period (HR 3.18, 95% CI 1.03–9.87) and decreased during the post-treatment period (HR 0.60, 95% CI 0.40–0.90) with a significant difference in HR between the two periods of follow-up (P=0.0066). Similar results were seen for subgroups of cerebrovascular diseases, such as stroke and ischaemic stroke. CONCLUSION: In an adjuvant setting, tamoxifen was associated with an increased risk of cerebrovascular disease during treatment, but a decreased risk in the post-treatment period.