Abstract Background: The ABCSG-12 trial demonstrated that adding zoledronic acid 4 mg IV q 6 months (ZOL) to endocrine therapy with goserelin 3.6 mg sc q 28 days plus tamoxifen 20 mg oral qd or anastrozole 1mg oral qd (ET) in premenopausal women with hormone receptor positive (HR+) early breast cancer (EBC) improves disease free survival versus ET alone. The objective of this study was to estimate the cost-effectiveness of ZOL in this setting from the perspectives of the healthcare systems in Sweden, Norway, Denmark, and Finland.Material and Methods: A Markov model was used to project lifetime outcomes and costs of breast cancer care for premenopausal women with HR+ EBC receiving 3 yrs of ET or 3 yrs of ET plus ZOL. Cost-effectiveness was measured as the incremental cost per quality adjusted life year (QALY) gained. Probabilities of breast cancer recurrence were based on ABCSG-12 (median [maximum] follow-up 48 [84] months). Probabilities and costs were from the published literature. Results were generated under 2 scenarios: (1) benefits of ZOL persist to the maximum follow-up in ABCSG-12 (trial benefits); (2) benefits persist until recurrence or death (lifetime benefits). Local currencies were converted to Euros to facilitate cross-country comparisons.Results: Expected costs of 3 yrs of ZOL q6m (medication and administration) were €1,869 for Sweden, €1,947 for Norway, €2,647 for Finland, and €2,824 for Denmark. Under the trial benefits scenario, these costs were partially offset by savings in the expected lifetime costs of treatment of breast cancer recurrence of €1,105 for Sweden, €1,422 for Norway, €1,400 for Finland, and €1,585 for Denmark. ZOL was therefore projected to increase total costs by €800 for Sweden, €559 for Norway, €1,247 for Finland, and €1,293 for Denmark. QALYs gained with ZOL were 0.37 in all settings. Cost per QALY gained was therefore €2,162 for Sweden, €1,510 for Norway, €3,369 for Finland, and €3,494 for Denmark. Assuming lifetime benefits, savings from preventing breast cancer exceeded additional costs of ZOL for all four countries, with net savings of €3,364 for Sweden, €4,736 for Norway, €3,753 for Finland, and €4,644 for Denmark. QALYs gained with ZOL were similar across countries, ranging from 1.22 to 1.24. ZOL was therefore a “dominant” strategy (more effective and less costly) in all settings under this assumption.Conclusion: Adding ZOL to ET in premenopausal women with HR+ EBC may be highly cost-effective (<€50,000 per QALY gained) from the healthcare system perspectives of Sweden, Norway, Finland, and Denmark even under conservative assumptions of the duration of ZOL benefit. Adding ZOL to ET leads to cost savings in all four Nordic countries if benefits observed in ABCSG-12 are assumed to persist until disease progression or death. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4088.