Estimating the benefits of adjuvant systemic therapy for women with early breast cancer

Background: Prognostic factors are commonly used to help identify women wit h node-negative breast cancer at high risk of recurrence. Although many are available, knowing which risk factor or combination of factors to use to e stimate prognosis for an individual woman is often difficult. This study do cumented the baseline prognoses for a group of women with node-negative bre ast cancers, and estimated the potential benefits of adjuvant systemic ther apy. Methods: Ten-year, actuarial, cause-specific survival based on tumour size and histological grade using data from the Swedish Two-County Trial of mammographic screening was calculated for 1200 women with node-negative ca ncers of less than 30 mm diameter. The benefits of adjuvant systemic therap y for these women were then estimated using the published odds reductions i n death from adjuvant systemic therapy from the Early Breast Cancer Trialis ts' Collaborative Group overview. Results: The absolute 10-year survival be nefits for subgroups of women based on tumour size and histological grade w ere estimated for women aged under 50 years by the addition of chemotherapy , and over 50 years by the addition of tamoxifen and/or chemotherapy. Concl usion: Decisions about adjuvant systemic therapy in women with node-negativ e breast cancer need to be individualized, taking into account treatment ef ficacy and toxicity. The quantitative methods presented in this paper facil itate such decisions.