Circulating Tumor DNA Mutations and Methylation Status as Biomarkers for Early Detection of Lung Cancer in Patients With Suspicious Lung Nodules

In Asia, the incidence and mortality of lung cancer are both high . The clinical demographics of lung cancer patients in Asia are different when compared with western countries. Both in Hong Kong and in Vietnam, there is a prominence of female non-smokers with lung cancer in Hong Kong, with a male: female ratio of 1.5:1. The biology of lung cancers arising from non-smokers are believed to be different from lung cancers from smokers. This is well reflected in the heterogeneity of lung cancer cell types and also their respective mutation profiles. For instance, there are more female non-smokers with lung cancer with the cell types of being adenocarcinomas, with about half in proportion of them carrying EGFR mutations; whereas in male smokers with lung cancer there are usually additional possibility of have squamous cell carcinomas, and the chance of the tumors carrying EGFR mutations is lower compared with non-smokers. Thus, different clinical biomakers should be used for early detection of lung cancer in smokers and non-smokers.

There is an urgent need to develop strategy for early detection of lung cancer in non-smokers who have no obvious risk factors like smokers. Blood-based biomarkers has the potential utility for identifying subjects with lung nodules showing high risk features for these lung nodules being malignant or becoming malignant, with whom additional workup for early diagnosis of lung cancer is indicated.

What are lung nodules with suspicious features of malignancy? Lung nodules are primarily defined by size of 3 cm or less. They may come in variable numbers or in different lung areas. The radiological appearance could be completely solid nodule (CSN), heterogeneous part-solid/part-ground glass nodules (hGGN) or pure ground glass nodules (pGGN). hGGN and pGGN have been shown to be more likely to be malignant compared to CSN. The presence of calcification, or simply radiological reporting to be granuloma, or fat density inside the nodule is known to indicate benign nature. Lung nodules with irregular or spiculated border are likely malignant whereas smooth border and roundish appearance usually indicates benign lesion. Thus, there is always an element of likelihood or probability of malignancy based on radiological appearance, but it is not possible to tell with full confidence, from imaging features, that a lung nodule is malignant or not.

With the often relatively small size and deep-seated location of lung nodules shown only on CT scan, invasive investigations for a lung nodule with tissue biopsy to confirm malignancy are associated with high morbidity. Non-invasive diagnostic biomarkers have become unique chance of improvement of risk management for subjects at risk. The challenges related to sorting out a large majority of benign nodules from malignant ones and among those a majority of aggressive from indolent cancers. The key questions in determining individual probabilities of diseases, given their history, findings on CT, and biomarkers of risk, remain most challenging. Appropriate risk assessment in reducing the false positives associated with current low-dose computed tomography practices and identification of individuals who need therapy and at what time during tumor surveillance could reduce costs and morbidities associated with unnecessary interventions.

Different blood-based biomarkers have been used alone or in combination in clinical practice. The most well-known one is Carcinoembryonic antigen (CEA). However, it is sensitive but not specific enough (raised level not limited to lung cancer but equally prevalent in colorectal tumor, and also inflammatory conditions). Newer biomarkers are urgently needed to enhance diagnosis of indeterminate or suspicious lung nodule.

Recently, the development of a multimodal assay called SPOTMAS Lung assay that simultaneously profile methylomics, fragmentomics, DNA copy number and end motifs in a single workflow of targeted and shallow genome-wide sequencing of cell free DNA with the aim of early detection of lung cancer. This assay has shown good diagnostic performance of overall sensitivity of 94% for detection of lung cancer.

Previous studies have shown that a quarter of patients with incidental pulmonary nodules experienced clinically significant distress that may relate to the poor knowledge about cancer risk and evaluation. Health care professionals have important roles to alleviate patients' distress through a good understanding on patients' level of understanding and distress related to the lung nodules and social support system. At the same time, it is important for physicians to know the applicability of available newer biomarker panels in different clinical situation to guide their respective clinical decision in further investigations.

The aim of this project is to use the assay of circulating tumor DNA mutations and methylomics to detect early lung cancer among subjects with suspicious lung nodules on lung imaging. The Key questions in determining individual probabilities of lung cancer, given their clinical history, findings on CT scan, and ctDNA mutation and methylation status for risk of early lung cancer, will be addressed. Reducing the false positives associated with current low-dose computed tomography practices and identification of individuals who need therapy and at what time during tumor surveillance could reduce costs and morbidities associated with unnecessary interventions.

Data will be collected and analysed according to the list of primary and secondary outcomes.

The primary outcome measure of the study is - the detection of ctDNA mutation and methylation in correlation with diagnosis of lung cancer or persistence of suspicious lung nodule.

The secondary outcome measures of the study are - the Sensitivity and specificity of clinical biomarkers in correctly identifying malignant lung nodule, i.e. lung cancer. The area under the summary receiver operating characteristic curve (AUC) and diagnostic odds ratio (DOR) with the ctDNA assay.

Improvement of positive diagnostic likelihood ratio (DLR+) and negative diagnostic likelihood ratio (DLR-) of using the in diagnosing lung cancer.

Cost-effectiveness in adding a clinical biomarker panel in enhancing risk stratification of lung nodules and hence diagnosis of lung cancer, defined as the incremental cost per additional lung cancer diagnosed.

The result from this project will provide means to early detection of lung cancer by ctDNA and methylomics assay. The Key questions in determining individual probabilities of lung cancer, given their clinical history, findings on CT, and ctDNA mutation and methylation status for risk of early lung cancer, will be addressed. Reducing the false positives associated with current low-dose computed tomography practices and identification of individuals who need therapy and at what time during tumor surveillance could reduce costs and morbidities associated with unnecessary interventions. The impact of psychological stress associated with the diagnosis and surveillance of lung nodules could also be evaluated.

The information gained from this project will provide evidence-based practice guidance for diagnostic evaluation for lung nodules or lung cancer.