gms | German Medical Science

Objectives: Metastatic disease is generally considered incurable. The aim of therapy is therefore usually disease control, prolongation of life and palliation of symptoms. The definition of "oligometastases" was first described in 1995 by Hellman and Weichselbaum as metastases limited in the number of metastatic sites and extent of disease. So far, different local treatment strategies for oligometastatic disease have been proposed, including radiotherapy, cryoablation, radiofrequency ablation and surgical metastasectomy. This type of therapy to control all known sites of disease is termed local consolidative therapy (LCT). The aim of this study was to analyze the available evidence for aggressive local treatment of oligometastatic disease.

Methods: A systematic literature research using PubMed with the search term "oligometasta*" was performed in order to identify all available studies dealing with oligometastatic disease. Since there is still no consensus on how many metastases the term "oligometastases" includes, it was decided to define it as a maximum of 5 metastases, which is in accordance with most studies in the literature. Only randomized controlled trials were included.

Results and conclusion: In total, six studies fulfilled the inclusion criteria. In all included trials, median progression-free survival (PFS) was longer in the aggressive treatment arm, ranging from 9.4 months to not reached in the treatment group versus 3.5 to 13 months in the maintenance group, respectively. Overall survival (OS) was surveyed in three studies and showed a significant benefit for patients treated with either radiotherapy or surgical metastasectomy, ranging from 41.2 to 50 months in the metastasis-directed therapy group versus 17 to 28 months in the surveillance group, respectively. However, no increase in overall survival could be reported for patients with cerebral oligometastases in non-small-cell lung cancer receiving stereotactic radiosurgery, with OS amounting to 14.6 months in the treatment arm versus 15.3 months in the surveillance arm. Altogether, no significant difference between surgical and radiotherapeutic metastasis-directed therapy could be detected.

In conclusion, aggressive local treatment of oligometastases is a promising therapeutic approach. As many different treatment modalities are in use, the foundation of treatment always has to contain a multi-disciplinary approach by specialists from different disciplines including medical oncology, radiotherapy, pathology, radiology and surgical or orthopedic oncology. Future randomized comparative studies are necessary to ascertain ideal timing and full impact of local therapy in treatment of oligometastatic cancer and determine its long-term efficacy and toxicity.