Reducing Cancer Side-effects With Systematic Light Exposure

Inclusion Criteria - Group 1: * High-risk breast cancer patients as defined by the Danish Breast Cancer Cooperative Group (DBCG) having received treatment according to the DBCG guidelines * Minimum age of 18 years; completion of adjuvant whole breast radiation treatments * A score \<34 on the FACIT-Fatigue scale (see below) after radiotherapy * Availability for home-based 4-week BWL/DL-treatment. Exclusion Criteria: * History of chronic fatigue disorders * Pregnancy * Confounding underlying medical illnesses such as significant pre-existing anemia * Diagnosed or suspected psychiatric or medical condition that might contribute to fatigue (other than those caused by the cancer or its treatment) * History of bipolar disease or mania (which are contra-indications for light treatment) * Current clinical depression * History of seasonal affective disorder * Previous diagnosis of sleep apnea, restless legs or other sleep disorders (not including insomnia) known to affect fatigue * Employment in shift work * Chronic use of oral steroid medication * Prior use of light treatment * Use of photosensitising medications * Plans to travel across meridians * Insufficient Danish language proficiency Inclusion criteria - Group 2: * Low-risk postmenopausal patients as defined by the DBCG having received breast-conserving surgery for lymph node-negative breast cancer * Completion of adjuvant whole breast radiation treatments * A score \<34 on the FACIT Fatigue scale (see below) after radiotherapy * Availability for home-based 4-week BWL/DL-treatment. Exclusion Criteria: * History of chronic fatigue disorders * Pregnancy * Confounding underlying medical illnesses such as significant pre-existing anemia * Diagnosed or suspected psychiatric or medical condition that might contribute to fatigue (other than those caused by the cancer or its treatment) * History of bipolar disease or mania (which are contra-indications for light treatment) * Current clinical depression * History of seasonal affective disorder * Previous diagnosis of sleep apnea, restless legs or other sleep disorders (not including insomnia) known to affect fatigue * Employment in shift work * Chronic use of oral steroid medication * Prior use of light treatment * Use of photosensitising medications * Plans to travel across meridians * Insufficient Danish language proficiency