In Sweden, every third person will be affected by cancer and the incidence is rising. This underscores the importance of both primary and secondary prevention. Breast cancer is the most common cancer in women living in Sweden, about 8000 women are diagnosed annually and 1400 eventually die of their disease. Most breast cancer patients receive adjuvant therapy. However, many are already cured by surgery and for some the therapy doesn’t work as intended. Body constitution, genetic, lifestyle and environmental factors modulate breast cancer risk and prognosis. Lifestyle can interact with therapy and affect drug response. Normal genetic variants are implicated in approximately 20% of inter-individual drug response, but this information is rarely used clinically. The group uses an integrative cancer epidemiological approach that combines information on host-, environmental-, and tumor factors in relation to outcome. We aim to generate evidence based lifestyle recommendations to be implemented in clinical practice for primary and tertiary prevention, and develop predictive tests for improved risk stratification and selection of therapy.