Lung cancer screening with low-dose computed tomography: A non-invasive diagnostic protocol for baseline lung nodules
Introduction
There were 100 million tobacco-related deaths in the 20th century, 1 billion deaths are expected in the 21st century, one third of which will be due to lung cancer. Lung cancer is the world's leading cause of cancer death [1], mainly because it is usually diagnosed at a regionally advanced or metastatic stage when incurable [2]. In western countries, including Italy, legal restrictions and campaigns against smoking are helping to reduce cardiovascular disease; however, the increased risk of developing lung cancer persists many years after stopping smoking [3]. Furthermore smoking is increasing among young people [4] and women in western countries, and across the board in developing countries [5].
Better detection of early lung cancers, especially in high-risk current or former heavy smokers, is an important part of the public health response to tobacco-related diseases. The most promising technique is screening with low-dose spiral computed tomography (LD-CT) [6], [7], for which pilot observational studies report high detection rates in high-risk populations: the proportion of stage I cases is high and survival is favourable compared to historical controls [8], [9], [10], [11]. However, non-calcified nodules are detected in a high proportion of screened subjects [12], [13]. Most of these are benign but may require invasive investigations, with high costs and attendant risks of complications; such cases may constitute an obstacle to the large-scale implementation of LD-CT screening [14].
In a pilot study with LD-CT at our Institute, 1035 volunteers were screened. The results were encouraging in that many detected lung cancers were at an early and resectable stage [15]. Our subsequent COSMOS (Continuous Observation of Smoking Subjects) study recruited more high-risk volunteers; one of its aims is to test non-invasive procedures to manage indeterminate screening-detected nodules, thereby contributing to the development of a protocol suitable for large-scale implementation.
The aim of the present paper is to evaluate the diagnostic performance of a non-invasive work-up protocol by analysing the results of baseline screening. A secondary objective is to assess the effectiveness of CT with contrast to evaluate solid nodules >8 mm.
Section snippets
Population and study design
In 2004 and 2005 we enrolled asymptomatic volunteers, age 50 years or above, who were current or former heavy (≥20 pack-years) smokers. Ex-smokers had stopped not more than 10 years previously. Those with malignant disease (except treated non-melanoma skin cancer) or a diagnosis of malignant disease within the previous 5 years were excluded.
This single-centre study was approved by the ethics committee of our institute. All recruited volunteers gave written consent to annual LD-CT for five
Results
From October 2004 to October 2005, 5201 eligible participants of mean age 57.7 years, standard deviation 5.6 years, underwent baseline LD-CT; 3437 (66.0%) were men, and 4164 (80.3%) were current smokers. The median number of pack-years smoked was 44 (range 20–255).
Table 1 shows characteristics of the baseline nodules according to age, sex and smoking status. A mean of 2.3 nodules/person was present in the 2754 volunteers with non-calcified nodules. Table 2 shows the characteristics of the
Discussion
The aim of LD-CT screening in high-risk populations is to reduce lung cancer mortality. However, to achieve this a sensitive protocol for detection, work-up and intervention, also characterized by contained costs and minimum morbidity must be developed. In the present study we present 1-year results (two screening scans) obtained using a non-invasive diagnostic protocol for managing lung nodules detected by annual LD-CT.
Our first important finding is that delay of malignancy diagnosis,
Conclusion
In this prospective study, we were able detect almost 70% lung cancers at stage I, using a protocol characterised by minimal subject recall, predominantly non-invasive case work-up, and low frequency of thoracotomy for benign disease. These outcomes support the feasibility of lung cancer screening in high-risk persons particularly in view of the promising finding of the recent I-ELCAP study, that screening-detected lung cancers have good survival [11]. However, further studies are required to
Conflict of interest
None of the authors have any conflict of interest to declare.
Acknowledgements
This study was supported by the Italian Association for Cancer Research (AIRC) and the America-Italia Cancer Foundation. We thank Giovanna Ciambrone for general management of COSMOS volunteers, Nicole Rotmentsz for designing the database, and Don Ward for professional help with the English (paid for by the European Institute of Oncology).
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