Introduction: Grief reactions of relatives of palliative care patients are seldom addressed. Most interventions focus on Prolonged Grief Disorder (PGD) and not on prevention. This is particularly relevant in palliative and advanced cancer contexts, in which death is the result of a difficult period of a terminal illness making caregivers particularly vulnerable to elevated psychological distress and PGD. Also, matched care interventions align with World Health Organization (WHO)'s (2009) guidelines for organizing mental health services. These guidelines, structured in a pyramid fashion ranging from low-intensity selective interventions and widely available to high-intensity specialized interventions, are tailored to citizens' needs. The differentiation of interventions allows combining need-based timely interventions to prevent PGD while increasing accessibility and mitigating inequality, through rationalization of service delivery.

Aims: The present research intends to implement and evaluate the effectiveness of the low-intensity selective intervention EMPOWER, compared to usual care, in terms of symptoms of prolonged grief and psychological distress in the population of family caregivers who lost a loved one in palliative and advanced cancer contexts. The second objective is to identify predictors of response to intervention. This research is crucial to influence national policy towards a greater emphasis on prevention and early intervention, making the allocation of cost-effective bereavement support services the most efficient and sustainable approach for a significant public health impact in bereavement care.

Procedures: Family members will be contacted from the Centro Hospitalar Universitário Lisboa Norte, by phone, following the usual practice of the clinical service. Those considered at risk, using the cut-off points of risk assessment to be at a moderate level, will be invited to additional intervention and participation in the current study. All participants will provide informed consent before being allocated to one of the two interventions. The informed consent process will cover the study's purpose, procedures, potential risks, and benefits, and it will be obtained from each participant before any data collection or randomization occurs. Participants will be reassured that their data will be anonymized and securely stored. Strategies to enhance participant retention and minimize attrition will be employed, including regular check-ins, reminders for follow-up assessments, a dedicated study coordinator to address participant concerns and flexible scheduling options. Also, a feedback system for participants to express concerns or provide input on the study's procedures will be put in place and this will be used to make necessary adjustments. Throughout their participation, we will emphasize participants' contribution to improving grief support for others and the rigorous privacy and confidentiality measures in place. Treatment will be offered at Centro Hospitalar Universitário Lisboa Norte, local health unit Santa Maria, to family members of patients followed on the palliative care unit and oncology service. To ensure fidelity and quality of intervention delivery across the team the standardized intervention protocol for EMPOWER will be utilized (manualized intervention); providers will receive standardized training and will have ongoing supervision; fidelity assessment tools will be used.

Trial design: a rater-blinded Randomized Controlled Trial (RCT) with two parallel groups, comparing the EMPOWER and treatment as usual (TAU) will take place in order to investigate a two-tier psychological intervention program designed to prevent PGD and offer early intervention for grief-related issues. Randomization will be independently conducted by a research assistant. Participants will be randomly assigned EMPOWER vs. TAU. Randomization will occur after a participant meets eligibility criteria, provides consent, and undergoes risk assessment. The participants will be allocated to each branch of the RCT through block randomization. A random sequence of numbers or allocation codes will be generated using a randomization tool. This sequence will determine the allocation of participants to the two intervention groups. To maintain allocation concealment, the randomization sequence will be securely locked away from researchers involved in recruitment and assessment. When a participant is deemed eligible and has provided informed consent, an independent staff member (or an automated system) not involved in day-to-day study operations will access the randomization sequence to assign the participant. Throughout the study, the project team will continuously monitor the randomization process to ensure it is executed as planned, with any deviations documented and addressed.