Evaluating Dose Timing (Morning vs Evening) of Endocrine-based Therapies in Metastatic Breast and Prostate Cancers

The REaCT-CHRONO-MetBP Pilot study will compare morning and evening administration of endocrine-based therapy in metastatic breast and prostate cancers. Participants with metastatic breast or prostate cancer will be randomly placed in one of two groups: a morning group and an evening group. The group assignment will determine whether they take their endocrine therapy in the morning or the evening. The primary outcome of this pilot study is to evaluate the feasibility of study procedures in order to conduct a larger definitive trial in the future. The secondary outcomes include comparing quality of life, tolerability, and efficacy outcomes between the morning and evening groups for each of the two cancer cohorts (metastatic breast and prostate cancer).

Cohort A (Breast Cohort) Inclusion Criteria * Patients with metastatic hormonal receptor positive breast cancer * Plan to receive endocrine therapy and a CDK4/6 inhibitor (either Ribociclib or Palbociclib) in the first-line metastatic setting * Age ≥18 years * Able to provide oral consent * Willing and able to complete questionnaires as per study protocol Cohort A (Breast Cohort) Exclusion Criteria * Any contraindication in taking endocrine therapy and CDK4/6 inhibitor in the morning or evening * Plan to receive abemaciclib (as this requires twice a day dosing) Cohort B (Prostate Cancer) Inclusion Criteria * Patients with metastatic castrate sensitive prostate cancer * Plan to receive androgen receptor pathway inhibitor (either enzalutamide, apalutamide or abiraterone acetate) in combination with androgen deprivation therapy * Age ≥18 years * Able to provide oral consent * Willing and able to complete questionnaires as per study protocol Cohort B (Prostate Cancer) Exclusion Criteria * Any contraindication in taking androgen receptor pathway inhibitor in the morning or evening * Plan to receive darolutamide (as this requires twice a day dosing) * Plan to receive docetaxel in combination with androgen receptor pathway inhibitor