(P-204) Use of Beta Blockers and Death from Breast Cancer in New Zealand Breast Cancer Patients

Background: Beta-blockers (BB), used for a range of cardiovascular indications, have been associated with improved cancer outcomes in international studies. This study examines the association between the use of BBs and death from breast cancer in New Zealand women.

Objectives: The primary objective of our study was to assess hazards of breast cancer specific mortality associated with beta-blocker use for patients with breast cancer.

Methods: Women who were diagnosed with breast cancer between 2007 and 2016 were identified from four population-based regional NZ breast cancer registries and linked to pharmaceutical data, hospital discharges, and death records. Median follow up time was 3.96 years. Cox proportional hazard models were used to assess the hazard of breast cancer specific death (BCD) associated with BB use.

Results: Of the 14,971 women included in analysis, 21% used a BB after diagnosis. Although not significant, beta blocker use increased the risk of BCD (adjusted hazard ratio: 1.15; 95% CI: 0.99-1.33). When considering subgroups however, the increased risk only remained in those with at least one cardiac condition, in patients under 80 years of age, and in those who were dispensed a BB in the last periods of life. When excluding dispensings in the six months prior to death/last follow up, the adjusted hazard ratio between BB use and BCD decreased to 0.95 (95% CI: 0.81-1.11). Risk was highest with short term use and decreased consistently with ever increasing doses.

Conclusions: The initial increased risk is likely to be due to confounding by indication, and there was a suggestion of a protective effect of long-term BB use on BCD.