SPP1 and squamous cell carcinoma: Multivariate survival analysis using the Cox regression model, which evaluated 7 factors, including gender, age (≤60 years vs > 60 years), smoking history (<20 pack year vs ≥ 20 pack year), histological type of lung cancer (adenocarcinoma vs squamous cell carcinoma vs adenosquamous carcinoma), regional lymph node stage (≤N1 vs > N1), number of extrapulmonary metastases, and SPP1 in MPE (low-SPP1-expressing vs high-SPP1-expressing), showed that SPP1 was an independent prognostic factor in patients with MPE associated with NSCLC (hazard ratio = 1.832, 95% CI = 1.003-3.345; P = 0.049) (Table 3).