This prospective observational study will evaluate quality of life, functional status, and cognitive outcomes in men with metastatic hormone-sensitive prostate cancer (mHSPC) receiving androgen receptor pathway inhibitors (ARPIs) in addition to standard androgen deprivation therapy. ARPIs in this study include abiraterone acetate, apalutamide, enzalutamide, and darolutamide, depending on local availability. A total of 102 patients will be enrolled from two academic oncology centers in Türkiye.

Participants will be assessed at baseline, 3 months, and 6 months using validated Turkish versions of established questionnaires: Functional Assessment of Cancer Therapy-Cognitive Function (FACT-Cog), Functional Assessment of Cancer Therapy-Fatigue (FACT-F), Patient Health Questionnaire-9 (PHQ-9), and Pittsburgh Sleep Quality Index (PSQI). Clinical parameters, ECOG performance status, routine laboratory results, and treatment-related adverse events will also be recorded.

The primary outcomes are longitudinal changes in FACT-Cog and FACT-F scores. Secondary outcomes include changes in depression, sleep quality, laboratory results, and adverse events. This study will provide real-world evidence on how ARPI therapy affects cognitive health and quality of life in patients with mHSPC.

Metastatic hormone-sensitive prostate cancer (mHSPC) is a disease stage in which systemic treatment strategies significantly affect survival, functional status, and quality of life. The incorporation of androgen receptor pathway inhibitors (ARPIs) into clinical practice has improved oncological outcomes, yet their influence on cognitive function, fatigue, mood, and sleep requires further real-world investigation.

In this study, the term androgen receptor pathway inhibitors (ARPIs) refer to abiraterone acetate, apalutamide, enzalutamide, and darolutamide. While abiraterone, apalutamide, and enzalutamide are widely used in routine practice in Türkiye, darolutamide may also be included when accessible. All patients will receive ARPIs in combination with standard androgen deprivation therapy (ADT).

This prospective, multicenter, observational cohort study will enroll 102 patients with newly diagnosed mHSPC at Ankara Etlik City Hospital and Gazi University. Assessments will take place at baseline, 3 months, and 6 months.

Validated Turkish patient-reported outcome instruments will be applied:

FACT-Cog: score range 0-148; higher scores = better cognitive functioning.

FACT-F: score range 0-52; higher scores = less fatigue.

PHQ-9: score range 0-27; cut-offs: 5 (mild), 10 (moderate), 15 (moderately severe), 20+ (severe depression).

PSQI: score range 0-21; global score >5 indicates poor sleep quality.

Additional measures will include ECOG performance status (0-5; higher = worse functioning), demographic and clinical characteristics, comorbidities, and routine laboratory tests. Treatment-related adverse events will be recorded according to CTCAE criteria.

The primary outcomes are longitudinal changes in FACT-Cog and FACT-F scores between baseline, 3 months, and 6 months. Secondary outcomes include changes in PHQ-9 and PSQI scores, ECOG performance status, and laboratory results, as well as adverse event profiles. Exploratory analyses will assess the relationship between clinical or laboratory variables and patient-reported outcomes.

Statistical analyses will include descriptive statistics, group comparisons, and repeated-measures modeling. Multivariable regression will be applied to identify predictors of impaired cognitive or functional outcomes.

By incorporating validated Turkish instruments and explicitly defining ARPI agents, this study aims to generate robust real-world evidence on the cognitive, functional, and quality-of-life effects of ARPI therapy in mHSPC. The findings are expected to guide supportive care strategies and optimize treatment decision-making.

Inclusion Criteria:

• Age ≥18 years
• Histologically or cytologically confirmed metastatic hormone-sensitive prostate cancer (mHSPC)
• Planned initiation of androgen deprivation therapy (ADT) plus an androgen receptor pathway inhibitor (abiraterone, apalutamide, or enzalutamide) as part of routine clinical care
• Ability to complete patient-reported outcome questionnaires (FACT-Cog, FACT-F, PHQ-9, PSQI)
• Written informed consent obtained

Exclusion Criteria:

• Prior systemic therapy for metastatic prostate cancer (except ≤3 months of ADT)
• Known history of severe cognitive impairment that precludes completion of questionnaires
• Concurrent active malignancy requiring systemic treatment
• Inability to comply with study procedures or follow-up
• Any condition judged by the investigator to compromise participation or data integrity

Only biologically male participants are eligible, as prostate cancer occurs exclusively in males. Self-identified gender does not alter eligibility since inclusion is based on biological sex.

Male patients aged 18 years and older with histologically or cytologically confirmed metastatic hormone-sensitive prostate cancer, initiating androgen deprivation therapy plus an androgen receptor pathway inhibitor (abiraterone, apalutamide, or enzalutamide) in oncology clinics. Participants will be consecutively enrolled at Ankara Etlik City Hospital and Gazi University Hospital.