The "PC-LIGHT" Study

Exclusion Criteria

• •History of light therapy use (e.g. systematic light exposure),
• •Active infection
• •History of chronic fatigue disorders
• •Confounding underlying medical illnesses such as significant pre-existing anemia (Hb\<10 gm/dl)
• •Diagnosed or suspected psychiatric or medical condition that might contribute to fatigue (other than those caused by the cancer or its treatment)
• •Hypothyroidism or documented history of hypothyroidism on thyroid replacement hormone within \<3 months of initiating RT
• •History of bipolar disorder or mania
• •History of seasonal affective disorder
• •Diagnosed sleep apnea, restless legs, or other sleep disorders (not including insomnia) known to affect fatigue
• •Use of photosensitizing medication
• •Plans to travel across more than 2 time zones during the study
• •Shift worker
• •Adults unable to consent, individuals who are not yet adults, pregnant women, and prisoners will be excluded from the study