Double-blind Randomized Controlled Trial Comparing Suvorexant 20 mg to Placebo for Treatment of Insomnia in Cancer Survivors

Investigators propose a double-blind, placebo-controlled trial evaluating the use of the use of Suvorexant in breast cancer survivors on selective estrogen receptor modulators or aromatase inhibitors with sleep disturbance to assess the impact on insomnia symptoms and quality of life. Breast cancer survivors have an increased risk of insomnia for which Suvorexant has the has the potential ability to impact to improve sleep related outcomes and cancer survivorship outcomes. Breast cancer survivors with sleep disturbance based on an Insomnia Severity Index Score (ISI) \>15 will be randomized to either Suvorexant or placebo, with both arms receiving education on sleep hygiene.

Inclusion Criteria: * Adult post menopausal breast cancer survivors (female, \> 18 years old) * current selective estrogen modulator or aromatase inhibitor use * at least 6 weeks beyond completion of definitive treatment for breast cancer * less than 5 years from time of diagnosis. Exclusion Criteria: * less than 6-month life expectancy * current steroid use * severe depression or anxiety * severe hepatic impairment * concurrent use of moderate or strong CYP3A inhibitors * current receipt of hospice care * severe mental illness * current use of greater than 40 morphine milligram equivalents daily * diagnosis of obstructive sleep apnea, narcolepsy or other sleep related illness other than insomnia * pregnancy * treatment with alternate pharmacotherapy for insomnia at the time of trial initiation * menstrual cycle within the past year