0358 Effects of Chronotype-tailored Bright Light Intervention on Post-Treatment Symptoms in Breast Cancer Survivors

Abstract

Introduction: Many cancer‐related symptoms emerge or amplify during cancer treatment and persist long after treatment terminates. Bright light therapy holds promise for reducing symptoms, e.g., sleep disturbance, that are commonly experienced by individuals with cancer. This study aimed to examine the effects of a chronotype‐tailored bright light intervention on sleep disturbance, fatigue, depressive mood, and cognitive dysfunction among post‐treatment breast cancer survivors. Methods: Thirty women with stage I‐III breast cancer 1‐3 years post‐completion of chemotherapy and/or radiation (mean age= 52.5 ± 8.4 years, 93% White) participated in this two‐group randomized controlled trial. Participants were randomized to receive either 30‐minute bright blue‐green light at 12,000 lux (intervention; n=15) or dim red light at 5 lux (control; n=15) daily for 14 consecutive days. Timing of light exposure, either between 19:00‐ 20:00 hours or within 30 minutes of waking in the morning, was tailored based on individuals' chronotypes (by Horne‐Ostberg Morningness‐Eveningness Questionnaire). Self‐reported symptom outcomes (e.g., sleep disturbance measured by Pittsburgh Sleep Quality Index) and in‐lab overnight polysomnography sleep study were assessed before (pre‐test) and after the 14‐day light intervention (post‐test). Linear mixed models (for continuous outcomes) or generalized estimating equations with cumulative log link function (for ordinal outcomes) were fitted to examine between‐group differences, while adjusting for correlation among repeated measures. Results: There were no significant between‐group differences in any of the symptom outcomes (all p>0.05). However, within each group, self‐reported sleep disturbance, fatigue, depressive mood, and cognitive dysfunction showed significant improvements over time (all p< 0.05); especially, the extent of improvement for fatigue and depressive mood was clinically relevant. Polysomnography sleep findings showed that number of awakenings significantly decreased (p=0.011) among participants receiving bright light, while stage 2 sleep significantly increased (p=0.015) among participants receiving dim‐red light. Conclusion: The findings support using light therapy to manage post‐treatment symptoms in breast cancer survivors. In contrast to our hypothesis, the study results are equally favorable to bright light and dim light condition. The unexpected symptom improvements among dim‐red light controls remain unexplained and requires further investigation.