Several oncologists have faith that cancers’ patients who register in clinical examination have better results as compare to who do not register. In this study, our objective is to assess the real evidence which such a trial impact exists. Accordingly, in the study, we established a conceptual structure for registered or non-registered patients’ comparison. We then confirm the inclusive study searching to analyze that our compared results are accurate between these two groups or not. We significantly evaluated these researchers to assess whether patients deliver valid and generalizable help for the impact of the trial. We analyzed 26 comparisons, these comparisons extracted from 24 already published articles of results among registered and unregistered patients in clinical trials. Accordingly, 21 comparisons utilized reflective cohort designs. In 14 comparisons there is provided accurate evidence which patient registered in trials and also have improved results. Therefore, approached to handle for probable confounding factors were represent unpredictable and often insufficient. Only 8 comparisons controlled the patients who were non-trial to those meeting the eligibility criteria of the trial. Of these, 3 prominent better results in trial patients as compared to non-trial patients. Patients with specific disease of hematological malignant and children with cancer and those patients who were treated before 1986 were excessively represented in positive studies. Despite enormous belief that registration in clinical examination further leads to enhance results in cancer patients, still, there are inadequate data to generate the result of that a trial effect occurs. As the prescribed data available, cancer patients must be encouraged to register in clinical examinations on the basis of the unquestioned role of examinations in enhancing treatment for coming patients.