Cancer related fatigue (CRF) is one of the most prevalent and distressing long-term complaints reported by (non-) Hodgkin survivors. The SPARKLE study will test the efficacy of two intensities of light therapy on cancer related fatigue. Additionally, it explores possible working mechanisms of light therapy on CRF including improvements in sleep quality, psychosocial variables (depression, anxiety, cognitive complaints, and quality of life), and changes in biological circadian rhythms.

Rationale: Cancer related fatigue (CRF) is one of the most prevalent and distressing long-term complaints reported by (non-)Hodgkin survivors. So far, there is no standard treatment. Some non-pharmacological interventions have shown large effects but show limitations as well, e.g. they are labor intensive. A novel and promising treatment for CRF is exposure to bright white light (BWL) therapy. This low-cost intervention is easy to deliver and has a low burden for professionals as well as for patients.

Objective: To examine the efficacy of BWL therapy as an intervention for CRF. As a secondary aim, this study will explore possible working mechanisms including changes in sleep quality, psychological variables, biological circadian rhythms, sleep-wake cycles, inflammation markers and genotype.

Study design: A multicenter randomized controlled trial will invite participants and allocate them to either a light intensity 1 condition (n=80) or a light intensity 2 condition (n=80). The longitudinal design will include four measurement points: baseline, mid-intervention, post-intervention, and at 3 and 9 months follow-up.

Study population: Hodgkin and diffuse large B-cell lymphoma (DLBCL) survivors fulfilling the clinical criteria of CRF and a survivorship of ≥ 3 years will be invited. Fatigue should not be attributable to a clear somatic cause or treatment for secondary cancer in the past year. Moreover, 25 Hodgkin survivors without CRF will be recruited to explore the association between circadian rhythms and CRF.

Intervention: The light intervention includes exposure to light for 30 minutes within the first half hour after awakening during 3,5 weeks.

Main study parameters/endpoints: The main study parameter in this study is the change in CRF from baseline to post-intervention and at 3 and 9 months follow-up. This will be assessed with the Multidimensional Fatigue Inventory.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Participation in this study includes completion of a light intervention for 3,5 weeks (30 min each day) and 2 visits (1h) to the treating hospital pre- and post-intervention. The visits aim to provide instructions and equipment and to collect two blood samples. Additionally, 5 saliva samples will be collected by the participant at home pre- and post-intervention. Moreover, participants complete questionnaires (30 min, 4 times) and wear an accelerometer (10d, 4 times and during light therapy) to objectively measure sleep quality and activity. Risks of the light intervention are limited, although there are few known reports of agitation, headache and nausea during the first days of light exposure. Benefits are the use of an easy to administer treatment for one of the most distressing symptoms that participants report.

Inclusion Criteria:

• A history of Hodgkin or DLBCL with a survivorship of ≥ 3 years.
• The presence of moderate to severe fatigue symptoms since diagnosis of or treatment for Hodgkin lymphoma or DLBCL.

Exclusion Criteria:

• Fatigue is explained by a somatic factor as defined in the guidelines of chronic fatigue syndrome of the Dutch internists association (NIV). When a somatic cause for fatigue is resolved by stable medication use ≥ 6 months, patients can be included in the current trial.
• Pregnancy (until 3 months postnatal) or women who provide breast feeding
• Extensive surgical operations in the past 3 months.
• Current diagnosis of a psychiatric disorder (e.g. personality disorders, psychosis, bipolar disorder) which would limit participation.
• Diagnosis of and treatment for a secondary malignancy in the past 12 months.
• Presence of photophobia (abnormal intolerance to visual perception of light) or another eye disease that shows symptoms of photophobia (e.g. aniridia, retinitis pigmentosa, glaucoma).
• Current or previous use of light therapy for more than 1 week.
• Current employment in shift work.
• Insufficient knowledge of the Dutch language.