SPP1 and small cell lung carcinoma: The serum OPN level before treatment in the SCLC group was (72.07 ± 19.09) ng/ml, while the 60 healthy controls was (36.06 ± 5.48) ng/ml, indicating that the serum OPN level of SCLC patients before treatment was significantly higher than that in the healthy controls (P = 0.000, Fig. 1A).