Very important conclusions for the early detection of lung cancer have been included in the recent publication summarizing the U.S. National Lung Screening Trial (NLST). This is the first study in which through the use of appropriate diagnostic methods managed to reduce mortality of patients with cancer of the lung. In this analysis supremacy of repeatedly performed low dose computed tomography (LDCT) over the standard chest x-ray was demonstrated. It is the first step, which in the future might allow the introduction of an effective screening program for lung cancer.

Mortality due to malignancies is one of the main causes of mortality of people today. Undoubtedly influence on this fact has the extension of average life span, improvement of the quality and availability of medical diagnosis as well as an increase in environmental pollution. As shown by the latest data published by the British Institute of Cancer Research UK from December 2011 on the epidemiology of cancer in the UK in the years 2008-2009, 75% of the new cases affects people aged over 60 years. The number of newly detected cancers in the UK is 310 thousand per year, and the number of deaths because of them is about 156 thousand. When we look at the detail, which tumors are responsible for the largest percentage of this mortality, in the first place definitely extends lung cancer. It provides up to 22% of all deaths (24% in men and 21% in women). The epidemiological situation in Poland is similar, also in our country, a lung cancer is the leading cause of death among malignancies. Unfortunately, such high mortality due to cancer of the lungs has remained constant for decades, and despite advances in medicine it cannot be reduced . Undoubtedly this is due to the detection of these tumors mainly in the III and IV stage, in which the percentage of the five-year survival is up to several percent.

The different situation is even with breast, colon or cervical cancer. In these neoplasm, mortality was significantly reduced in the last 20-30 years. This decrease resulted from the successful implementation of effective screening programs for early detection of these tumors (respectively mammography, colonoscopy and cytology of cervical smear). By definition the screening is carried out in populations characterized by a higher probability of tumor incidence but who had no symptoms indicating the presence of cancer. Early detection is especially important in the case of tumors which have a high mortality rate. One of these neoplasm undeniably is lung cancer. Screening tests should be safe for patients, cheap, readily available, easy to do and possible to widely perform. In the context of the above cited data on lung cancer it seems reasonable to place questions: Is there currently any method for early detection of lung cancer? Is it possible to implement it as a screening test, which would significantly reduce mortality due to this tumor?

The first attempts to conduct research on early detection of lung cancer were performed in the seventies of the twentieth century. They used chest x-ray and sputum cytology. These examinations were performed repeatedly, respectively every 12 and 4 months. Increased detection of lung cancer was achieved in patients undergoing both radiological and cytological examinations, but this did not translate into a difference in mortality between these patients. It was similar in both groups.

With the development of medical imaging techniques, in the nineties have been attempts to use low dosage computed tomography (LDCT) in the early detection of lung cancer. LDCT protocol reduces radiation dose to 25% received in a standard chest tomography. This is very important for the safety of patients. Excessive exposure to radiation may result in dangerous complications, including even the development of secondary tumors. Research from the end of the twentieth century due to the low numbers of patients, did not give a clear answer whether application of the LDCT may influence in the reduction of mortality of patients with lung cancer.

Compared with existing observations, a very promising are the results of NLST study published in August 2011. This is a multicenter study conducted since 2002, comparing the effectiveness of LDCT and chest x-ray as methods for early detection of lung cancer. In this study, 53 454 patients aged 55-74 years with a history of smoking of at least 30 pack-years and without previously recognized cancer of the lung were randomized. Then 3 tests at annual intervals (LDCT or chest x-ray depending on the assigned group) were performed in each patient. By 2009 the observation of the patients was conducted by assessing the incidence of lung cancer and mortality due to malignancies. During the study, the incidence of lung cancer detection in both groups was similar (1060 vs 941), while these groups significantly differed in mortality of patients. Among patients in whom LDCT has been performed, up to 20% lower mortality due to lung cancer than in the group of patients with the chest x-ray was observed (247 vs 309). These initial reports show a real chance that in the future, with appropriate qualifications of screened patients undergoing LDCT could be introduced as a screening test for lung cancer. After analyzing the results of the NLST study, also raises some doubts. They concern the very large percentage of false-positive results, which were respectively 96,4% for LDCT and 94.5% for x-ray. Also the number of tomography examinations needed to perform to prevent one death from lung cancer of 320, makes that the costs of such proceedings are very high.

So the question arises, which country would be able to introduce of such form of screening tests to the main panel. Perhaps further requests from the NLST study, concerning on various biochemical markers, will give us more information and allow better detection of lung cancers in their early stages of development.

Written by: Dominik Cieniawski

Source:
1. http://info.cancerresearchuk.org/cancerstats/mortality/
2. Laprus I., Adamek M., Kozielski J.: Potrzeba badań przesiewowych w kierunku wczesnego wykrywania raka płuca – nowe dowody, nowe nadzieje. Pneumonol. Alergol. Pol. 2011; 79:419-427
3. National Lung Screening Trial Research Team, Aberle DR., Adams AM., Berg CD., Black WC., Clapp JD., Fagerstrom RM., Gareen IF., Gatsonis C., Marcus PM., Sicks JD.: Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med. 2011; 365:395-409br>


Want to know more about lung cancer? Watch on medtube.net: Adenocarcinoma – Histopathology – Lung.