Prognostic factors of oligometastatic non-small cell lung cancer: a meta-analysis.

Background: The prognostic factors of oligometastatic non-small cell lung cancer (NSCLC) are uncertain. We performed a meta-analysis to assess the prognostic factors of oligometastatic NSCLC patients who are most likely to achieve long-term survival.

Methods: We searched PubMed, EMBASE, the Cochrane to identify eligible articles and performed the meta-analysis of all randomized controlled trials (RCTs) and retrospective comparative studies revealing the prognostic factors of oligometastatic NSCLC. The primary endpoint of interest was overall survival (OS).

Results: We analyzed data from twenty-four eligible studies, including data from 1,935 patients with oligometastatic NSCLC. In the univariate analysis, we found no significant difference in OS of prognostic factors including age [hazard ratios (HRs) 1.02, 95% CI: 0.80-1.31, P=0.86], smoking status (HR 1.08, 95% CI: 0.80-1.46, P=0.62), type of metastases (HR 1.61, 95% CI: 0.86-3.03, P=0.14), but significantly positive prognoses containing female (HR 1.21, 95% CI: 1.02-1.45, P=0.03), (y)pN0 stage (HR 1.82, 95% CI: 1.40-2.36, P<0.00001), adenocarcinoma (HR 1.44, 95% CI: 1.10-1.88, P=0.008). In the multivariate analysis, patients with (y)pN0 stage had an obvious survival benefit compared with (y)pN1 (HR 1.63, 95% CI: 1.27-2.10, P=0.001), but no significant survival in contrast with (y)pN2 (HR 2.01, 95% CI: 0.80-5.03, P=0.14). In subgroup analyses, neither thoracic stage (HR 2.06, 95% CI: 1.52-2.78, P=0.55), (y)pT-stage of primary lung cancer (HR 1.38, 95% CI: 0.86-2.21, P=0.14) nor tumorous histology (HR 2.99, 95% CI: 2.10-4.28, P=0.91) and oligometastatic number (HR 1.25, 95% CI: 0.97-1.62, P=0.98) were significantly different in OS. However, patients with aggressive thoracic treatment (ATT) had improved survival (HR 0.56, 95% CI: 0.37-0.83, P=0.001), and notably, different strategies of ATT received by oligometastatic NSCLC patients might significantly influence survival (HR 0.54, 95% CI: 0.36-0.82, P<0.00001).

Conclusions: Overall, factors including age, smoking status, type of metastasis were not associated with long-term survival of oligometastatic NSCLC patients. However, our finding suggests that aggressive therapies in the primary lung cancer, as well as female, (y)pT-stage, absence of nodal diseases, adenocarcinoma histology have been clarified as positive prognosis. Further studies of prospective study for these patients are warranted.