Current and future research efforts in oligometastatic non-small cell lung cancer-a systematic review.

Background: Major progresses in the systemic treatment of non-small cell lung cancer (NSCLC) were obtained during the last decade, including the use of immunotherapy and tyrosine kinase inhibitors (TKIs), with impressive results in terms of response and survival rates. Moreover, novel imaging and radiotherapy techniques have allowed the development of stereotactic body radiotherapy (SBRT), with high rates of local disease control and minimal toxicity. These factors propelled the use of combined systemic and local treatment strategies in patients with a low burden of metastases-the oligometastatic disease (OMD).

Methods: We systematically review the evidence from prospective randomized and non-randomized trials on local ablative therapy for OMD NSCLC published until June 2020. In addition, we present a review of the ongoing and/or recruiting trials in the field.

Results: We included 16 articles, reporting on 14 prospective clinical trials, starting from the pilot trial conducted in the early 2000's to the recent randomized trials that have showed benefits in survival. We found 24 ongoing trials, which combine multiple local ablative regimens with new systemic therapies, such as new generation TKIs and immunotherapy.

Discussion: Despite these vast current and ongoing prospective research efforts, there are several issues that impair the generalizability of their findings. These include the heterogeneous definition of OMD, trial design, staging, patient selection, tumor mutational status and treatments used, which may limit their applicability in the clinical practice.