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

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.

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).

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).

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.