This prospective, non-randomized, single-center observational study is designed to investigate the effects of oral versus intravenous (IV) 5-fluorouracil (5-FU)-based adjuvant chemotherapy regimens on sleep quality and depression levels in patients with non-metastatic gastrointestinal system (GIS) cancers.

Eligible adult patients (aged 18 years or older) who are scheduled to receive adjuvant chemotherapy at the Ankara Etlik City Hospital Medical Oncology Department will be assessed using the Pittsburgh Sleep Quality Index (PSQI) and the Beck Depression Inventory (BDI). These evaluations will be conducted at baseline (prior to chemotherapy), on day forty-five, and on day ninety of treatment.

This study will not interfere with standard oncologic care. Instead, sleep disturbances and depressive symptoms will be monitored during routine clinical follow-up. Patients identified with significant psychological distress will be referred to psychiatry or sleep medicine departments for further evaluation.

The results of this study may provide insights into how different routes of 5-FU administration impact patients' mental health and quality of life, potentially informing future supportive care strategies during adjuvant chemotherapy.

This is a prospective, non-randomized, single-center observational study designed to investigate the effects of oral versus intravenous (IV) 5-fluorouracil (5-FU)-based adjuvant chemotherapy regimens on sleep quality and depression levels in patients with non-metastatic gastrointestinal system (GIS) cancers.

The study will be conducted at the Ankara Etlik City Hospital, Medical Oncology Department. A total of 100 adult patients (≥18 years) who are initiating adjuvant chemotherapy including 5-FU (either oral or IV formulation) for histopathologically confirmed non-metastatic GIS cancers will be included.

Eligible patients will be enrolled after providing informed consent. The Pittsburgh Sleep Quality Index (PSQI) and Beck Depression Inventory (BDI), both of which have been validated in Turkish, will be used to assess sleep quality and depression severity. These measurements will be obtained at three time points: (1) baseline (prior to chemotherapy initiation), (2) day 45, and (3) day 90 of treatment.

The study aims to detect early psychosocial changes that may occur during chemotherapy, particularly those related to sleep and mood. No changes or interventions will be made to the patients' standard oncological treatment. Patients showing severe sleep disturbances or depressive symptoms during follow-up will be referred to the relevant departments (psychiatry or sleep medicine) for further evaluation and care.

The goal of the study is to better understand how the route of 5-FU administration (oral vs. IV) influences sleep patterns and emotional well-being during adjuvant chemotherapy. This could help optimize supportive care strategies and improve the quality of life of patients undergoing treatment for GIS cancers.

Data will be analyzed using appropriate statistical tests. Categorical variables will be compared using Chi-square or Fisher's exact test; continuous variables will be compared using Student's t-test or Mann-Whitney U test, depending on distribution. A p-value of <0.05 will be considered statistically significant.

Inclusion Criteria:

• Histopathologically confirmed non-metastatic gastrointestinal system cancer (e.g., colorectal, gastric)
• Age ≥18 years
• Planned to receive adjuvant chemotherapy containing 5-FU (either oral or IV)
• ECOG performance status 0-2
• Provided informed consent

Exclusion Criteria:

• Patients with psychiatric disorders affecting sleep or mood
• Receiving treatment for primary sleep disorders or depression
• Prior chemotherapy or radiotherapy for the current diagnosis
• Inability to complete the questionnaires due to cognitive or language barriers

Adult patients diagnosed with non-metastatic gastrointestinal cancers who are receiving adjuvant chemotherapy with oral or intravenous 5-fluorouracil-based regimens at a tertiary cancer center.

Individual participant data (IPD) will not be shared due to local data protection regulations, ethical restrictions, and the absence of prior consent for data sharing.