397P - Survival of de novo metastatic breast cancer according to biomarker status in Denmark and Norway: A register-based cohort study

Background

In the Nordics, new treatments have emerged, offering targeted therapies tailored to the specific pathophysiology of breast cancer (BC). These therapies are more effective with fewer side effects than conventional chemotherapy. It's crucial to monitor treatment trends, effectiveness, patient selection, and safety closely. The current study aims to study usability and coverage of real-world data among patients with BC in Norway and Denmark with focus on biomarkers in de novo metastatic BC (mBC).

Methods

BC patients were identified in national administrative registers in Denmark and Norway from January 1, 2015 to December 31, 2020 and followed until death or end of follow-up, i.e., December 31, 2021. Patients were categorized according to stage and biomarker status (hormone receptor (HR) and HER2). Descriptive statistics and one-year survival analyses based on Kaplan-Meier were carried out stratified per country, stage and biomarker status.

Results

In total, 51,641 patients with BC were identified (Denmark: 29,392; Norway=22,249), of which 1,988 (3.8%) had mBC at time of diagnosis (Denmark=946 (3.2%); Norway=1,042 (4.7%)). The age at time of diagnosis of mBC was 68.4 in Denmark and 64.4 in Norway. The number and proportions with HR and HER2 combinations in Denmark and Norway, respectively, were HR+/HER2+ 103 (11%) and 58 (5.6%), HR+/HER2- 608 (64%) and 426 (41%), HR-/HER2+ 51 (5%) and 70 (6.7%), HR-/HER2- (i.e., triple negative) 101 (11%) and 102 (10%), not tested 83 (9%) and 386 (37%). One-year survival was highest among mBC patients with HR+/HER2+ status (Denmark= 0.73 (95% confidence interval (CI), 0.65-0.82); Norway= 0.86 (95% CI, 0.80-0.95)) and lowest among those with triple negative mBC (Denmark= 0.52 (95% CI, 0.44-0.63); Norway=0.51 (95% CI, 0.41-0.62)) as expected.

Conclusions

Results are overall in agreement between the two countries with high coverage. This unique data will later be combined with treatment records and becomes highly valuable for real-world evidence studies of targeted treatments in patients with BC.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Quantify Research.

Funding

Has not received any funding.

Disclosure

J. Liseth Hansen: Other, Institutional, Other, Quantify Research provide consultancy services to pharmaceutical companies and other private and public organizations and institutions: Multiple. M. Johnsen: Other, Institutional, Other, Quantify Research provide consultancy services to pharmaceutical companies and other private and public organizations and institutions: Multiple. F. Fischer: Financial Interests, Institutional, Other, Quantify Research provide consultancy services to pharmaceutical companies and other private and public organizations and institutions: Multiple. O. Ström: Financial Interests, Institutional, Other, Quantify Research provide consultancy services to pharmaceutical companies and other private and public organizations and institutions: Multiple. T. Kopp: Other, Institutional, Other, Quantify Research provide consultancy services to pharmaceutical companies and other private and public organizations and institutions: Multiple.