The purpose of this study is to verify clinical utility of a simple blood test comprising of four protein- based markers for risk stratification of patients presenting symptoms related to lung cancer.

The study is a multicenter, prospective case-control research. Totally 1,200 cases will be collected in the hospitals, with 600 cases in control group, which are not suspected as lung cancer from chest CT, and other 600 in suspected group. When inclusion into the two groups, clinical information and 10mL blood sample of the patient will be recorded and tested for cancer biomarkers, biochemical detection and cardiovascular disease biomarkers, etc. The correlation between cancer biomarker panel, CT scan result and clinical pathological diagnosis will be investigated through cases follow up. The sample size estimated above was set up according to sensitivity and specificity of biomarkers in pre-study, based on lung cancer incidence of the population. To compare the diagnostic accuracy among different cancer biomarkers through T-test, Mann-Whitney U and receiver operating characteristic (ROC) curve with SPSS 15.0 software. In statistic analysis, 0.05 is set as the p value for significance. Effectiveness of the four biomarkers panel in lung cancer diagnoses and staging will be analyzed.

Inclusion Criteria:

• Non-suspected lung cancer group (600 cases)

  1. Aged 40 to 75 years;
  2. Male smoker (≥400 cig/year), female smoker or non-smoker;
  3. Visible lung nodule lesion in the chest (based on local CT result);
  4. Without the indication of biopsy (bronchoscope or percutaneous transthoracic) or surgery.

• Suspected lung cancer group (600 cases)

  1. Aged 40 to 75 years;
  2. Male smoker (≥400 cig/year), female smoker or non-smoker;
  3. Visible lung cancer lesion in the chest (based on local CT result);
  4. With the indication of biopsy (bronchoscope or percutaneous transthoracic) or surgery.

Exclusion Criteria:

• Histopathological diagnosis result is unavailable, including patients only have cytology results of pleural effusion;
• Already treated by chemotherapy or surgery

Totally 1,200 cases will be collected in the hospitals, with 600 cases in control group, which are not suspected as lung cancer from chest CT, and other 600 in suspected group.