Role of radiotherapy in the treatment of CUP syndrome

Background CUP (cancer of unknown primary origin) is defined as a heterogeneous group of cancer diseases. The diagnosis of metastatic cancer of unknown primary is associated with uncertainties of both diagnostic and therapeutic nature in everyday oncology practice. Methods Based on literature reviews as well as clinical expertise, the options for radiation treatment in CUP were described. Results Histology, location and extent of tumor manifestations are crucial for planning radiotherapy. Indispensable for targeted and effective radiotherapy are modern imaging techniques for pretherapeutic staging and target volume definition. In combination with surgical and drug approaches, radiotherapy opens up therapeutic possibilities for organ-preserving and curative procedures in axillary and cervical CUP. In palliative situations, radiotherapy offers options for prevention and treatment of disease-associated complications and maintenance of quality of life (e.g., osseous and cerebral metastases). Conclusions The treatment of patients with CUP syndrome presents an interdisciplinary challenge. Radiotherapy offers curative therapy approaches for localized CUP. It is effective in symptomatic metastases.