Naltrexone RCT for Treatment-Emergent Fatigue in Patients Receiving Radiation Therapy for Breast Cancer

This trial has two phases (a monitoring and an intervention phase). Monitoring Phase: Prior to starting radiotherapy for non-metastatic breast cancer, participants will be approached and consented for the monitoring phase of the study, which involves longitudinal monitoring of fatigue in order to establish whether a patient develops fatigue after starting radiation. The level of pre-radiotherapy fatigue will be obtained during the final two weeks before radiotherapy is started. All participants will undergo weekly monitoring of fatigue via a brief self-report questionnaire. The monitoring period will continue up until one month after the conclusion of radiotherapy. Those whose fatigue symptoms increase above the pre-specified threshold at any point during the monitoring period will be approached about enrollment into the intervention phase of the study. Intervention Phase: This is a randomized, double-blind, parallel-arm 5-week clinical trial which will be used to determine the effect of naltrexone on fatigue emerging during radiation therapy for non-metastatic breast cancer.