The utility of six serum tumor markers in early detection of lung cancer


 Background: Lung cancer has become the leading cause of cancer-related death in China. However, most of patients were diagnosed at advanced stage. Thus, novel lung cancer diagnostic tests, which can be used to screen individuals in early stage, are required.Methods: A total of 208 patients involving 161 cases of lung cancer and 47 cases of benign diseases were enrolled. Serum concentration of GTM, CETM, PTM, CTM, ETM and HTM were analyzed by kits according to the manufacturer’s guidelines.Results: The results showed significant difference in serum concentrations of GTM, CETM, PTM, CTM, ETM, and HTM between patients with lung cancer and benign diseases. In addition, when compared with benign diseases, higher levels of those six markers were also observed in patient with SCC and SCLC, but not for ADC. Receiver operating characteristic (ROC) curves were further suggested a high sensitivity and specificity of six markers to identify lung cancer.Conclusion: The serum levels of GTM, CETM, PTM, CTM, ETM and HTM in lung cancer were significantly higher than those of benign diseases. Moreover, these six biomarkers showed a high sensitivity and specificity to identify a patient with malignant. These findings suggested that detection of those six biomarkers in serum might be helpful for differential diagnosis of lung cancer.

higher than those of benign diseases. Moreover, these six biomarkers showed a high sensitivity and specificity to identify a patient with malignant. These findings suggested that detection of those six biomarkers in serum might be helpful for differential diagnosis of lung cancer.

Background
Lung cancer has become the leading cause of cancer-related death in China, occupying approximately 25 percent of morality rate.(1),(2) Quantities of smokers, mostly are youth and middleaged population, leads to steadily growth of pulmonary tumor incidence and mortality rate each year.
(1),(3) Because of lacking typical clinic symptoms, over 80% cases diagnosed at advanced stage and missed proper therapy. (3) Studies have demonstrated that five-year survival rate was just 4% in cancer metastases patients, much less than non-invasive ones whose living percentage went up to 55% after surgery.(4) Low-dose computed tomography (LDCT) was recommended to high risk individuals for its reduction of 20% mortality when compared with traditional chest X-ray.(3), (5) However, its low specificity of 60% and accumulate radiation risk eliminated potential priority in widely single use for lung cancer screening. (5) Recently, advanced detection technology in analyzing the progress of tumor initiation and development had found series of tumor proteins, genomics and proteomics. Some molecular biomarkers, including autoantibodies against tumor-associated antigens (TAAs)(6), (7), microRNAs (8), (9), and circulating tumor cells (10), presented considerable potential to the discovery of early-stage cancer. However, majority of tumor markers could not be widely used due to the low sensitivity and specificity. We therefore performed this study to evaluate the levels of six indicators (GTM, CETM, PTM, CTM, ETM, HTM) in serum for differential diagnosis of lung cancer.

Methods Subjects
In our study, patients were enrolled from Ningbo First Hospital from June 2017 to February 2018. They were 18 age or older, no acute disease before hospitalization, and were found lung lesion or pulmonary nodules by CT scan. Those who had other malignant tumors, accepted anti-tumor therapy before surgery, merged with autoimmune system disease, pregnant or renal failure, were excluded for minimizing the effect to investigation results. The enrolled patients were finally confirmed by surgery and pathological analysis. The study protocol was approved by the Institutional Review Board wavelength to 450, 442, 406, 420, 470,486 nm respectively. By adjusting to zero value with distilled water, the absorbance of each tube is detected. Each marker is calculated by multiplying the absorbance ratio (measuring / calibration-mean) by 100 to get the final results.

Statistical analysis
Basic characteristics of patients' data were presented as the means ± standard error of the mean (SEM), and chisquare test was performed to compare the distribution of categorical variables. The levels of every tumor marker conformed to normal distribution, and the student's t-test was taken to verify the existence of differences in statistics, while comparison among three pathology types of tumor was conducted by Kruskal-Wallis one-way ANOVA test and illustrated as inter quartile ranges (IQR) and median. A P value was calculated in two-tailed and expressed statistical differences when it was less than 0.05. Receiver operating characteristic (ROC) curves were constructed to evaluate the diagnostic value of each tumor marker, the corresponding sensitivity, specificity, the area under the curves (AUC) and 95% confidence intervals (CI) were calculated. The optimum cut-off point was chosen by assessing two items: likelihood ratio and the maximum value of the sum of specificity and sensitivity. The process of data analysis was operated on GraphPad Prism 5.0 (GraphPad Software, San Diego, CA, USA).

Patients
A total of 208 patients were enrolled in this study and basic characteristics were summarized in   1D). ETM also presented intense and statistical significance in the discrimination of lung cancer from benign groups (106.9 ± 1.4 U/ml vs 96.5 ± 1.5 U/ml, P = 0.0002, Fig. 1E). HTM showed higher concentration in lung cancer than that in benign diseases (65.0 ± 0.9 U/ml vs 58.9 ± 1.6 U/ml, P = 0.0009, Fig. 1F).

The diagnostic value of six serum tumor markers in lung cancer
The results of previous analysis have illustrated that GTM, CETM, PTM, CTM, ETM and HTM have the potential to become novel tumor markers for screening lung cancer. Then, we constructed ROC curves to assess the diagnostic value of these six serological indicators (Table 2) (Fig. 3E). Comparing lung cancer patients with benign ones, the AUC of PTM for lung cancer were 0.6445 (95% CI, 0.5637-0.7253) in the threshold value of 83.55 U/ml (Fig. 3C), and the utility of HTM is relatively low with the area of 0.6493 (95% CI, 0.5690-0.7297) for distinguishing lung cancer from benign diseases (Fig. 3F).  Table 2.

Discussion
Currently, the diagnosis and management of lung cancer are still in intractable challenges worldwide. In order to achieve the early detection of screening lung cancer, it is necessary to take actions in the pre-cancerous and diagnoses in early stages. (11) For high risk population whose smoking pack-years over thirty in the past or at present, blood testing was recommended as the assistance for chest imaging examination with minor trauma instead of continual CT scan(11),(12), (13). CT scan showed a low specificity for lung cancer screening. (6), (14) We therefore performed this study to estimate the clinical value of six tumor markers in discriminating lung cancer from benign diseases.
The results showed higher concentration of GTM, CETM, PTM, CTM, ETM and HTM in patients with lung cancer than those with benign diseases, which may be useful for recognizing pulmonary malignant. Moreover, when lung cancer was classified into the pathological subtype groups, statistically significant differences in the serum levels of six biomarkers were observed in the comparison with benign diseases. Each marker showed considerable sensitivity and specificity for recognizing patients with SCC and SCLC. For adenocarcinoma, GTM, PTM, CTM, ETM and HTM were significant increased in cancer patients, which was not found in CETM.
GTM showed the highest sensitivity of 63.35% and specificity of 72.34%, with the under area of 0.6840 by ROC curves, to differentiating lung cancer from benign diseases. Similar results were also observed for CETM, PTM, CTM, ETM and HTM in differential diagnosis of lung cancer. It has been reliably proved that GTM was closely related to tumor initiation and invasion (15), (16), (17). In this study, its utility for screening malignant cancer was

Conclusions
To the best of our knowledge, this is the first study for these six tumor markers to identify lung cancer from benign diseases. Our study showed the serum levels of GTM, CETM, PTM, CTM, ETM and HTM in lung cancer were significantly higher than those of benign diseases. Moreover, these six biomarkers showed a high sensitivity and specificity to identify a patient with malignant. These findings suggested that detection of those six biomarkers in serum might be helpful for differential diagnosis of lung cancer.

ETHICS APPROVAL AND CONSENT TO PARTICIPATE
The study protocol was approved by the Institutional Review Board of Human Studies of Ningbo First Hospital.
The written informed consent to participate in the study was be obtained from all participants.

CONSENT FOR PUBLICATION
Not applicable.

AVAILABILITY OF DATA AND MATERIALS
All the data supporting our findings can be found in the results section of the paper.

COMPETING INTERESTS
The authors declare that they have no competing interests.