Radiotherapy for oligometastatic non-small cell lung cancer: a narrative review

Preclinical and early clinical evidence suggest that radical radiotherapy of oligometastatic disease in non-small cell lung cancer (NSCLC) patients can impact outcomes with relatively limited toxicity. Whilst data from phase 2 randomized trials suggesting an improved overall survival (OS) with this treatment is promising, it has also illustrated the heterogeneity in this patient population and treatment. Oligometastatic disease in itself comprises a broad spectrum of patients, in terms of tumor load and location, stage of the disease and treatment history. This real-life variety in patient characteristics is often reflected in studies to a certain extent, hinting to the fact that all might benefit from radical radiotherapy to limited metastatic disease, yet leaving the question unanswered as to whom the ideal candidate is. Furthermore, differences between and within studies with regards to treatment modality, timing, radiation technique, and radiation dose are substantial. Also, preclinical and early clinical trials suggest that radiotherapy can work synergistically with checkpoint inhibitors by acting as an in situ cancer vaccine, therefore the combination of these two treatments in oligometastatic patients might entail the largest benefit. Ongoing randomized controlled phase 3 trials and prospective registry trials will further elucidate the true extent of benefit of this local treatment strategy and aid in identifying the ideal patient population and therapy. The current narrative review summarizes the clinical evidence on radiotherapy for oligometastatic NSCLC and highlights the remaining unknowns.