After the cutoff points of individual numerical parameters were determined by ROC analysis, multivariate analysis using binomial logistic regression identified high serum KL-6 (OR 3.68, p = 0.027), initial PSL dose (OR 4.18, p = 0.013), combination therapy (OR 5.51, p < 0.001) and male sex (OR 3.38, p = 0.024) as independent risk factors for serious infections. This evidence concerns the gene MUC1 and infection.