553 Background: Anthracycline chemotherapy is used frequently in adjuvant breast cancer treatment but there is clinical trial evidence of cardiac toxicity. Attempts to quantify this risk in routine care have been limited by follow up time & confounding factors. The aim of this project was to exploit rich Scottish NHS datasets for this purpose. Methods: Patients treated surgically for stage I-III invasive breast cancer between 2000 & 2010 were identified from a local cancer database (Edinburgh Cancer Centre). Outcomes were captured by linkage to the Scottish Morbidity & death Records. Follow-up was until March 2016. The primary outcome was a cardiac event or cardiac death, identified from coding. Analysis used the Latouche approach (estimating cause-specific hazards & sub-distribution hazards) for the primary outcome & the competing risks of death from breast cancer & death from other causes. Results were adjusted for age, deprivation (SIMD), co-morbidity (Charlson), year of diagnosis, side of radiotherapy, cancer stage, grade, ER & HER 2 status. Results: 4080 patients were identified, 1658 received an anthracycline containing regime, 297 received non-anthracycline chemotherapy & 2125 received no chemotherapy. A total of 33946 women years were analysed. During median follow up of 8.2 years there were 448 cardiac events & 559 breast cancer deaths. After adjustments there was no association between anthracycline use & cardiac outcomes (HR 0.9, 95% CI 0.67-1.21). There was an increased risk of breast cancer death (HR 1.66, 95% CI 1.28-2.16).Age & Charlson score were associated with an increased cardiac risk. Stage & grade were statistically associated with breast cancer death. Conclusions: No increased risk of cardiac events was seen in women treated with anthracyclines, they can be safely used in carefully selected patients. This data suggests selection may be over-cautious, a lower threshold for treatment may lead to improved breast cancer outcomes. Rich routine health datasets & appropriate analysis methods make outcomes monitoring feasible in Scotland. Oncologists are skilled at assessing both cardiac risk factors & breast cancer risk.