Background and Rationale: Cancer patients receiving outpatient therapy often manage complex medication regimens that include anticancer agents, supportive care medications, and treatments for chronic comorbidities. This polypharmacy greatly increases the risk of medication discrepancies, potential drug-drug interactions, and unintentional errors. Moreover, because most oncology care is delivered in outpatient settings, patients are primarily responsible for self-administering their medications, making adherence a key determinant of treatment success and patient safety (Lindenmeyer et al., 2022; Alshehri et al., 2024). Medication errors and poor adherence among oncology patients are widely recognized global concerns. Research indicates that nearly half of cancer patients experience at least one medication discrepancy during transitions of care, and nonadherence to oral anticancer therapies can exceed 40%. Such issues can result in reduced treatment efficacy, increased toxicity, avoidable hospitalizations, higher healthcare costs, and poorer quality of life (Weingart et al., 2018; Wu et al., 2020; Patel et al., 2021). Pharmacists, as essential members of the multidisciplinary oncology team, are uniquely positioned to address these medication-related challenges. Their pharmacotherapy expertise and patient-education roles enable them to detect discrepancies, optimize medication use, and enhance patient understanding of treatment regimens. Evidence from various healthcare settings shows that pharmacist-led interventions such as medication reconciliation, individualized counseling, and structured follow-up can improve medication safety and adherence (de Clercq et al., 2021; Boeni et al., 2022). Despite strong evidence supporting each of these interventions individually, few studies have examined the combined effect of pharmacist-led reconciliation, counseling, and follow-up in outpatient oncology practice. Adult cancer patients face additional challenges, including complex dosing schedules, emotional distress, and financial burdens, all of which can impair medication adherence. An integrated pharmacist led program may create a continuous safety net that detects medication discrepancies early, reinforces correct use, and sustains adherence throughout treatment (Gellad et al., 2022; ISPOR Report, 2023). Therefore, this study aims to evaluate the impact of a comprehensive pharmacist-led program encompassing medication reconciliation, individualized counseling, and systematic follow-up on enhancing medication adherence and reducing medication errors among adult outpatient cancer patients. Demonstrating the effectiveness of this integrated care model may provide strong evidence to support the routine inclusion of pharmacists in outpatient oncology services to improve patient outcomes and medication safety (Alshehri et al., 2024; Boeni et al., 2022).

Study Hypothesis: Adult oncology outpatients are frequently prescribed complex medication regimens upon leaving the hospital. Therefore, this study aims to evaluate whether a comprehensive pharmacist-led outpatient program improves medication adherence and reduces medication errors among this population.

Inclusion Criteria:

• • Adult medical oncology outpatient at NCI, Cairo University with different diagnoses.

  • Receiving ≥5 medication

Exclusion criteria:

• Cognitive impairment,
• Palliative care
• Language barriers