A guideline for screening distress in patients with cancer has been published in the Netherlands. Use of the distress thermometer (DT) is recommended. However, the effects of the use of the DT on the psychosocial wellbeing of the patient as well as the cost-effectiveness are unknown. A 2-arm randomized controlled trial is performed in patients treated for primary breast cancer to assess these effects of the nurse-led intervention (systematic use of the DT and its discussion by a nurse) compared to usual care provided to outpatients by their physicians. In the experimental arm the DT is collected from and discussed with patients by a trained nurse. If necessary, patients are referred to an expert professional depending on the problems encountered. In the usual care arm, no DT is used and patients are referred to an expert professional if this is felt necessary by the treating physician. All patients diagnosed with primary breast cancer who will be treated with curative intent are eligible and invited. Recruitment takes place in the out-patient clinic of a university hospital. In total, 193 patients is needed. Primary outcome measure is quality of life measured with the EORTC QLQ C30. Questionnaires are obtained in both arms after completion of each treatment modality and during follow up (first year every 3 months, second year every 6 months). Patients are followed from diagnosis until two years after finishing treatment. This study is currently recruiting participants. At this moment there are 143 participants in the study. We expect completion of accrual in November 2012.The preliminary results of the measurements during treatment will be presented. So far as we know, this is the first randomized controlled longitudinal study about the effects of the DT as a nurse-led intervention.