BACKGROUND: When D-dimer value increasing, first of all suggests the possibility of clotting disorders and venous tromboembolism, cardio vascular diseases. Cancer and other disorders must be considered ıf there is no thromboembolic diseases. METHODS: Histopathologically diagnosed stage III-IV cancer patients have d-dimer values who undergone radiotherapy were included in this study. Key woeds: d-dimer, cancer, radiotherapy Ethical approve: Ethical approve was taken from ethical board of Başakşehir Çam and Sakura City Hospital Conflict of Interst: There is no any conflict of interest between persons or companies.