Sixten's research centers on breast cancer survivorship, exploring the relationships between obesity, circulating lipids, metabolism, and the recurrence and survival of breast cancer. Sixten examines prognostic factors related to obesity and metabolism, aiming to provide clinicians with insights into lifestyle-associated elements that require intervention to mitigate the risk of breast cancer recurrence. The research also delves into the repurposing of drugs and pharmacological interventions to reduce recurrence risk and improve survival in breast cancer patients.

Sixten's epidemiological research is primarily conducted within the Danish Breast Cancer Groups clinical registry and the Malmö Diet and Cancer study, utilizing extensive datasets encompassing data from 50,000 to around 110,000 individuals. As an MD-PhD fellow at the Medical and Graduate School of Health at Aarhus University, Sixten conducts research under the supervision of Chair Professor Signe Borgquist. In addition to research dedication, Sixten is involved in teaching and mentoring medical students at the Faculty of Health at Aarhus University and participates in various Danish and international networks focused on obesity and cancer research.

Sixten's primary research focus revolves around unraveling the intricate connections between obesity and metabolism and their impact on breast cancer survivorship. Committed to employing pioneering epidemiological and clinical research methodologies, Sixten collaborates closely with national and international experts, with the overarching objective of making meaningful contributions to the field of oncology and enhancing the prospects of survival for individuals facing breast cancer.