Popularizing summary One of the possible treatments for cancer, is radiation therapy. Previously, patients got smaller doses in more visits, because this seemed to be better in minimizing side effects. Imaging and radiation techniques, among others, improved over the years and the interest in higher doses in less visits grew. This decreases the patients practical burden by decreasing the number of visits and increases disease control of the irradiated lesion in the same time. An interesting use of the these high doses is treating disseminated lesions in patients with only a few lesions. For these patients, also called oligometastatic patients, a great interest in curative treatments is nowadays investigated. The few lesions form multiple targets for treatment, which requires accurate radiation therapy for avoiding adverse events caused by irradiation on neighbouring organs. For this treatment, we need to be able to select those patients who would benefit from radiation therapy on the disseminated lesions. A suggested classification system distinguishes patients with a history of multiple disseminated lesions that were partially controlled by chemotherapy or another sort of systemic therapy, patients who have a history of a few lesions and patients who did not have disseminated lesions, but now do. There are also patients who already had disseminated lesions at the first diagnosis of cancer. Another distinction that can be made in the former mentioned three categories is whether the disseminated lesions were growing while under some sort of systemic therapy or not, or whether they remain more present than other lesions. For this thesis, oligometastatic patients receiving radiation therapy on disseminated lung, abdominal lymph node and adrenal lesions were gathered from a list and information was collected from patient files. The results of the overall selected patient population conformed approximately to existing literature, confirming the curative potential of highly dosed radiotherapy in oligometastatic patietns. After performing statistics, the results pointed in the direction of a better survival of patients who did not have lesions in their history, compared to patients who had multiple lesions in their history and patients with lesions which grew under systemic therapy had a less favourable survival. Patients with disseminated lesions at first cancer diagnosis had a relatively less favourable survival, but when surviving, the treated lesions remained stable for longer. This classification can already distinguish different types of patients, but the effects of other factors on survival and other patient outcomes are still to be investigated more. This thesis attempted to study the effect of lesion location, number of treated lesions, number of treatments and dose. The only significant observation is the more favourable survival of patients with abdominal lymph node compared to lung and adrenal lesions. Social relevance This thesis results can impact treatment decisions of clinicians about patients with only a few disseminated lesions. More specifically, oligometastatic patients with a curative potential can be selected for treatment and patients without a curative potential will not be bothered with unnecessary treatments. The most important idea still is the curative potential for these patients, when they were previously only treated with palliative purpose.