ImportanceImplementation of guideline-recommended depression screening in medical oncology remains challenging. Evidence suggests that multicomponent care pathways with algorithm-based referral and management are effective, yet implementation of sustainable programs remains limited and implementation-science guided approaches are understudied.ObjectiveTo evaluate the effectiveness of an implementation-strategy guided depression screening program for patients with breast cancer in a community setting.Design, setting, and participantsA pragmatic cluster randomized clinical trial conducted within Kaiser Permanente Southern California (KPSC). The trial included 6 medical centers and 1436 patients diagnosed with new primary breast cancer who had a consultation with medical oncology between October 1, 2017, through September 30, 2018. Patients were followed up through study end date of May 31, 2019.InterventionsSix medical centers in Southern California participated and were randomized 1:1 to tailored implementation strategies (intervention, 3 sites, n = 744 patients) or education-only (control, 3 sites, n = 692 patients) groups. The program consisted of screening with the 9-item Patient Health Questionnaire (PHQ-9) and algorithm-based scoring and referral to behavioral health services based on low, moderate, or high score. Clinical teams at tailored intervention sites received program education, audit, and feedback of performance data and implementation facilitation, and clinical workflows were adapted to suit local context. Education-only controls sites received program education.Main outcomes and measuresThe primary outcome was percent of eligible patients screened and referred (based on PHQ-9 score) at intervention vs control groups measured at the patient level. Secondary outcomes included outpatient health care utilization for behavioral health, primary care, oncology, urgent care, and emergency department.ResultsAll 1436 eligible patients were randomized at the center level (mean age, 61.5 years; 99% women; 18% Asian, 17% Black, 26% Hispanic, and 37% White) and were followed up to the end of the study, insurance disenrollment, or death. Groups were similar in demographic and tumor characteristics. For the primary outcome, 7.9% (59 of 744) of patients at tailored sites were referred compared with 0.1% (1 of 692) at education-only sites (difference, 7.8%; 95% CI, 5.8%-9.8%). Referrals to a behavioral health clinician were completed by 44 of 59 patients treated at the intervention sites (75%) intervention sites vs 1 of 1 patient at the education-only sites (100%). In adjusted models patients at tailored sites had significantly fewer outpatient visits in medical oncology (rate ratio, 0.86; 95% CI, 0.86-0.89; P = .001), and no significant difference in utilization of primary care, urgent care, and emergency department visits.Conclusions and relevanceAmong patients with breast cancer treated in community-based oncology practices, tailored strategies for implementation of routine depression screening compared with an education-only control group resulted in a greater proportion of referrals to behavioral care. Further research is needed to understand the clinical benefit and cost-effectiveness of this program.Trial registrationClinicalTrials.gov Identifier: NCT02941614.