Inclusion Criteria:  Female patient with histologically proven breast cancer Indication for radiotherapy Sleep disorders (i.e. at least 2 points on the sleep disorder self-rating scale) Eastern Cooperative Oncology Group (ECOG) performance score 0-2 Age ≥18 years Written informed consent Capacity of the patient to contract  Exclusion Criteria:  Pregnancy, Lactation Expected non-compliance (patient unable to use the seizure diary)