Of the 96 patients with SCLC, 66 were male and 30 were female, with a median age of 55 years. Fifty-eight patients had a history of smoking, 38 had no history of smoking, 28 had limited SCLC, 58 had extensive SCLC, and 70 had lymph node metastasis. Most patients (n=80) received EP chemotherapy and radiotherapy (n=86). After treatment, 78 cases were CR or PR, and 18 cases were SD or even PD (Table 1). The median follow-up time was 12 months (2-30 months), the median OS was 11 months, the limited- stage SCLC was 14 months, and the extensive SCLC was 8.5 months.
Upregulation of serum OPN level in SCLC patients
The pre-treatment serum OPN levels in SCLC group were (72.07±19.09) ng/ml, compared with (36.06±5.48) ng/ml in the 60 healthy controls, indicating that the pre-treatment serum OPN levels were significantly higher in SCLC patients than those of the healthy controls (P=0.000, Fig. 1A). However, the levels of serum OPN were downregulated after treating the patients with chemoradiotherapy (72.07±19.09 pg/ml vs. 61.69±10.42 ng/ml, P=0.019, Fig. 1B).
Association of pretreatment levels of serum OPN with clinicopathological features from SCLC patients
We plotted the ROC curve to assess the cut-off value of pre-treatment serum OPN levels and found that 38 ng/ml is the cut-off value for serum OPN levels. We then analyzed the relationship between OPN expression and clinicopathological features in patients with SCLC. Our data showed that serum OPN levels were closely related to disease stage (P=0.012), tumor size (P=0.034), and lymph node metastasis (P=0.037) (Table 2).
Association of serum OPN levels with treatment response
The objective response rate (CR+PR) after chemotherapy and radiotherapy was 81.2% (78 of 96 cases), and the non-response rate (SD+PD) was 18.8% (18 of 96 cases). We then correlated serum OPN levels with treatment response and found that serum OPN levels were significantly associated with treatment response after treatment (P=0.011, Fig. 2A); however, pretreatment serum OPN levels were not significantly associated with treatment response (P=0.485, Fig. 2B).
Prognostic value of serum OPN for SCLC patients
We performed univariate and multivariate analyses to predict prognostic factors for OS in these patients. Our univariate analysis data showed that performance status, disease stage, and post-treatment serum OPN levels were prognostic factors for OS, and our multivariate analysis showed that performance status, disease stage, and post-treatment serum OPN levels were all prognostic predictors for OS of these patients. However, pre-treatment serum OPN levels were not associated with OS in these patients (Table 3).
We also used Kaplan-Meier curves and log-rank tests to correlate post-treatment serum OPN levels with OS in these SCLC patients and found that the reduced post-treatment level of serum OPN was associated with better OS of these SCLC patients (Fig. 3).