The screening of any disease refers to identifying the disease occurring before the symptoms begin. The primary aim of screening lies in disease detection at the initial and most treatable stages of the disease. The medical practitioners accept different screening programs involving several criteria, such as reducing the mortality rate concerned with the particular condition. The screening tests usually consist of lab tests that aim to check the blood and other fluids, genetic tests for finding out the inherited genetic markers showing association with the disease, and imaging exams that mainly evolve pictures explaining the body anatomy. The screening tests are available primarily to every general individual. Different factors such as age, gender, and family history are responsible for carrying out particular screening tests per the individual’s requirement.
The suspected individuals of lung cancer have been observed at high risk to lung cancer development with no signs and symptoms of the disease while undergoing low-dose computed tomography (LDCT) scanning of the chest portion. LDCT mainly combines the special x-ray equipment with sophisticated computers for producing multiple cross-sectional images or pictures within the inner sections of the body. The LDCT is involved in the image production of sufficient quality to detect the abnormalities with the utilization of 90% less ionizing radiations when compared with that of the conventional chest C.T. scan.
The previous screening methods of lung cancer included chest x-ray and sputum cytology to diagnose the occurrence of lung cancer. Chest x-ray has evolved the images of the heart, lungs, airways, blood vessels, and the spine and chest bones. Sputum cytology has been used as the lab test where a sample of sputum (mucus coughed from the lungs) is tested and viewed under a microscope for identifying the cancerous cells. But, the utilisation of chest x-ray and sputum cytology, whether carried out individually or in combination, have not shown effective results in reducing the risk of mortality rate due to lung cancer.
Several organizations have considered the scientific evidence and the risks and benefits of screening lung cancer. These organizational groups have evolved screening recommendations for individuals who are more at risk of developing lung cancer. Hence, the suggestions of screening methods keep on varying as per the organizational norms. The most common screening technique for lung cancer is the low-dose helical or spiral computed tomography (C.T. or CAT) scan that involves taking pictures of the inside region of the body with an x-ray machine and later combining with the computer to produce precise details, the 3-dimensional image representing any abnormalities or tumors. But, CT scanning may not be recommended for everyone who has the habit of smoking. Some of the screening recommendations for lung cancer involve approved and experienced centres which Medicare later approves.
The clinical outcome for non-small cell lung cancer (NSCLC) is directly associated with the stage of diagnosis of the disease while evolving the significance to the screening modality resulting in the detection of lung cancer among the individuals. The lung cancer screening utilizes chest radiographs or sputum cytologic analysis, failing to provide mortality benefits in various clinical trials 1,2. Several other lung cancer screening methods have been integrated with appropriate analysis of the most effective screening method. The National Lung Screening Trial has evolved the computed tomography (C.T.) and compared with radiography while involving a total of 53,454 patients who were at higher risk, and the result revealed that lung cancer mortality benefit of 20% and a 6.7% decrease in all-cause mortality 3. The U.S. Preventive Services Task Force has suggested annual screening with chest low-dose C.T. in high-risk individuals to lung cancer belonging to the age group of 55 to 80 years with non-continuous screening once it is clear that the individual has not adopted the habit of smoking since 15 years and has a limited life expectancy 4. The conduction of another major trial of screening for lung cancer includes the randomized low-dose CT-based lung cancer screening trial that involved the 15,822 individuals who were found to be former smokers in the Netherlands and Belgium and were compared to low-dose C.T. at different screening intervals with varying years with no screening. Hence, this screening method resulted in a 26% reduction in the deaths due to lung cancer, mainly among high-risk men at 10-year follow-up 5,6,7.
Although the screening as mentioned above methods have shown efficacy in reducing the death rates of patients who have lung cancer, still some of the screening methods of lung cancer have demonstrated non-effective results with the emergence of significant challenges such as insurance coverage and secondary costs, increasing rates of false-positive results, ill-effects of radiation exposure, stressed out conditions of the patient due to the continuous follow-ups since longer duration, and the risk of overdiagnosis in a population at increased risk for other potentially life-threatening comorbidities, mainly in the case of smokers 8. Several controversies have evolved in the adoption of lung cancer screening methods, mainly among individuals with a history of smoking who have quit the smoking habit for more than 15 years, along with management of false-positive test results. Hence, there is a need for identifying more effective screening methods for reducing the death rates due to lung cancer.
The conduction of clinical screening trials has been performed to determine the screening methods’ effectiveness in reducing the mortality rate at effective cost. The Eastern Cooperative Oncology Group and the American College of Radiology Imaging Network (ECOG-ACRIN) have shown the results of the screening trials while integrating the use of imaging tests for screening the disease identification among the affected individuals. The National Cancer Institute has revealed the information regarding the clinical trial that involves the studies related to both cancer screening and treatment methods.
The current suggestions regarding the screening for lung cancer have involved the publication of a large, randomised clinical trial being sponsored by the National Cancer Institute, mainly known as the National Lung Screening Trial (NLST). The primary aim of NLST is to determine the level of reduction of death rates due to lung cancer by integrating screening low-dose chest C.T. exams among the individuals who are majorly at higher risk for the disease. This screening method has included more than 53,000 men and women aged 55 to 74 and was found to be current or former heavy smokers. These participants were randomly assigned to receive screenings with low-dose C.T. (LDCT), or standard chest x-ray performed once every year for three consecutive years. As a result, this screening trial showed 15%-20% slower death rates in lung cancer among the screened participants with LDCT.
Depending upon the results of NLST and other related studies, the National Comprehensive Cancer Network, American Lung Association, American Association for Thoracic Surgery, American College of Chest Physicians, American Thoracic Society and the American Cancer Society have suggested the fact that individuals who are at high risk for developing lung cancer choose yearly screening with LDCT. The U.S. Preventive Services Task Force (USPSTF) contributes to integrating the screening trials while suggesting annual screening for lung cancer with LDCT among adults 50-80 years old. They have a smoking history of almost 20 pack-years and have now quit smoking for the past 15 years. The pack-years mainly refers to multiplying the number of cigarette packs smoked per day by the number of years smoked by the individuals.
Lung cancer screening is mainly carried out by conducting several programs by the medical professionals and facilities with expertise in LDCT screening and multiple specialities such as pulmonologists, radiologists, interventional radiologists, thoracic surgeons, and medical professionals oncologists, primary care doctors and pathologists involved in lung cancer. The lung cancer screening method is not an alternative for quitting smoking, as eliminating the smoking habit is the best preventive measure against lung cancer.
The conduction of C.T. scanning and LDCT shows similarities with other x-ray examinations evolving the examination of the body in the form of radiative images. The LDCT for lung cancer does not require any contrast material. This screening method is integrated by positioning the back on the C.T. exam table while using straps and pillows to help the individuals maintain the appropriate positioning and remain still during the screening process. Later, the raising of arms overhead is guided by the technician. The table then moves quickly towards the scanner for determining the appropriate starting position for the scans. The table is moved slowly through the machine while the individuals are advised to hold their breath for each short 5-10 second scan.
Lung cancer is often detected while identifying the lung nodule, the region of abnormal tissue within the lung. The nodules mainly represent the region scarring within the lungs from prior infection or small lymph nodes rather than representing cancer. In the case of LDCT scanning of lung cancer, this screening method can detect the nodule larger than the expected size. The specialist mainly suggests the follow-up LDCT scan several months later to check the nodule for not changing its size. Suppose the nodule grows in size as per the suspicious cancer cells. In that case, the specialists suggest evaluating advanced imaging studies using contrast-enhanced C.T. or removing a small piece of the nodule known as lung biopsy. Later, the pathologists can analyze the biopsy results under the microscope, whether the nodule is malignant (cancerous) or benign. If the nodule is cancerous, the doctors will suggest blood and imaging tests to determine the tumor stage. The imaging tests consist of the additional C.T. scanning of the body and PET/CT scan.
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