Remarkably, the incidence of gastrointestinal cancer cases among cancer types is increasing. Gastrointestinal cancers are one of the 10 most common cancer types in the World. This increase worldwide is remarkable, especially due to the increase in urbanization, consumption of foods rich in animal fat, insufficient dietary fiber intake and lifestyle changes. Cytotoxic therapy, which is used in the treatment of malignant diseases, can cause serious complications in gastrointestinal cancer, distinguishing it from other types of cancer. In addition, patients experience symptoms such as nausea-vomiting, mucositis, diarrhea, and constipation much more severely due to the direct effects of these agents on the gastrointestinal system. For this reason, patients\' compliance with the treatment process and their quality of life are seriously affected, and patients have difficulties especially in meeting their self-care needs. The aim of this project is to evaluate the effects of self-care deficit care model and mobile application-supported care on symptoms and quality of life of patients with gastrointestinal cancer.

Material and method: The research was conducted as a experimental study. The universe of the research; Between Feb 2022 and Jan 2023, individuals who met the criteria for inclusion in the study who applied for home care to Erzurum Atatürk University Research Hospital Oncology Clinic with the diagnosis of gastrointestinal cancer. The sample size for the research was determined by power analysis. In the power analysis, it was determined that a total of 52 people should be reached in order to reach the 95% confidence level at the 0.05 significance level and 80% power at the p\<0.05 significance level. Considering that there may be data losses in the study, it was decided to reach 60 people, 15% more than the sample. The patients included in the study were determined as intervention (n=30) and control (n=30). During the data collection process, 4 patients, 1 in the control group and 3 in the experimental group, died and the study was completed with the results of 29 control and 27 intervention group patients. "Patient Description Form" from the intervention and control group to determine the current physical and psychological self-care needs of patients with gastrointestinal cancer, "Edmonton Symptom Assesment Scale" physical symptoms experienced by patients, and "Quality of Life Scale" for psychological symptoms and the "Self care ability scale" for self care ability was used to collect information. Permissions for use were obtained for each of the scales. In the analysis of data; percentile distribution, chi-square, Fisher-Freeman- Halton Exact test, t-test in independent groups, Repeated Measures ANOVA Test, Friedman Test, One Way ANOVA test, Kruskall Wallis test, and post hoc analyzes (Bonferroni, Games Howell, Dunn) were used.

In the intervention group, symptoms on the ESAS improved significantly. The EORTC QLQC30 functionality and symptom sub-dimensions improved significantly. In the control group, the severity of symptoms increased and quality of life decreased compared to baseline measurements. While self-care competence increased significantly in the experimental group, there was no change in the control group. The need to develop \"common language, common care\" practices in oncology clinics, accompanied by an evidence-based guide, is also a priority in patient care. The results of this study showed that mobile app-supported Orem's care can effective on patients\' symptoms, and self care ability.