Diagnostic procedures

Early Diagnosis

When talking about early diagnosis the meaning of a few basic concepts has to be emphasised.

PRIMARY PREVENTION means reducing the risk factors known for a specified disease. Thus, in the case of lung cancer, primary prevention consists mainly in antismoking and tobacco habit campaigns (nicotic weaning campaigns) and in implementing the control of risk factors in the working environment.

SECONDARY PREVENTION includes all the programmes aiming at identifying the disease in the early stage and in the absence of its signs or symptoms. An example of secondary prevention is the Pap test for uterine carcinoma.

TERTIARY PREVENTIONmeans preventing the onset of a second tumour in a person already treated for another tumour. It is carried out through periodic examinations and follow-ups planned by the reference oncologist. Screening programmes fall within secondary prevention procedures. The ultimate goal of screening programmes is to obtain a fall in mortality for a specified disease, that is a definite reduction in the number of deaths related to such an illness. In the ’70s studies were conducted on healthy subjects (mostly heavy smokers) using chest x-ray, but no study among those carried out showed a mortality reduction for such a disease in the population being examined. The same deceiving results were obtained with the performance of the sputum cytology (i.e. the search for tumour cells in the catarrh). The introduction of spiral CT (computed tomography) scan arose many hopes about this technique and its possible application in early diagnosis. The spiral CT scan allows to acquire in a unique lung ventilation (thanks to a computed reconstruction of the image) a clear representation of the thorax, improving the examination reliability and reducing radiation exposure. Spiral CT scan is a highly sensitive and specific technique thanks to its capacity of minimising artefacts (or better the alterations of images) caused by respiration. Furthermore the technique allows a relatively low dosage of radiations: 0.75 mSv (millisievert, measure unit used to evaluate radiation exposure versus 1 mSv of the simple chest x-ray.

Spiral CT scan can record also minimum differences in density among tissues (for example fluid/solid) and allows the detection of elements which otherwise could not be seen by x-ray only. In the last few years several studies have been conducted using spiral CT scan as screening examination in subjects having a ‘high risk’ to develop a lung neoplasm (thus heavy smokers). The choice of population is based on the fact that no data are still available showing unquestionably a fall in mortality for lung neoplasm thanks to the use of this system of diagnosis. It is sure that spiral CT scan succeeds in identifying more frequently and precisely the presence of small lung nodules (diagnostic superiority). It has to be emphasised, however, that most of such nodules are NOT diagnosed as tumours. In the American study ELCAP (conducted by Claudia Henske and published in 1999 in The Lancet) the yearly performance of a spiral CT scan of the chest was compared with the simple chest x-ray. The study was carried out on a sample of 1,000 high risk subjects and a clear diagnostic superiority was proved for spiral CT scan versus chest x-ray. Another example with similar results is the Japanese study (conducted and published in Kaneko, Radiology in 1996) on a population of 1,369 high risk subjects submitted to a spiral CT scan or chest x-ray every 6 months for a certain number of years.

From 2000 to 2005 also in our Hospital a programme of early diagnosis was carried out on 520 asymptomatic volunteers having a high risk of developing a lung carcinoma. These persons yearly underwent a spiral CT scan of the chest for five consecutive years. Awaiting the consolidated results on the role of spiral CT scan in the reduction of mortality for lung cancer (the results will come from large world studies presently under way), there are still many ‘dark’ points in planning a screening for lung cancer.

A number of difficulties are still present in:

- identifying and studying small size (millimetric) nodules

- determining the nature of non-solid nodules at lung level

(also called ‘ground-glass opacity’ or GGO)

- defining the frequency of performance of CT scan

(every year, every two years…)

- defining the age of start and the length of the screening

(for example starting from the age of 50 and for how many years?)

- defining exactly the characteristics of the subjects under study with the screening (the entire population or only smokers / people having had or being under an occupational exposure to potentially carcinogenic material).

In Italy, at the Istituto Nazionale dei Tumori of Milan, the project MILD (Multicentric Italian Lung Detection), co-ordinated by Ugo Pastorino, M.D. (green number 800.21.36.01; www.progettomild.org) is under way.

The goal of the project is to evaluate if the periodic examination of the chest through spiral CT scan, in association or not with other advanced diagnostic methods, is capable of reducing lung cancer mortality in high risk subjects, that is heavy smokers or ex-smokers having ceased smoking from at least 10 years, aged between 49 and 75. The volunteers enrolled are randomly assigned to two groups: a control group undergoing the pneumologic visit and the spirometric exam (an exam assessing the lung function that is the ‘respiratory capacities’ of a subject) also submitted to a programme of primary prevention providing help to cease smoking and a second group combining primary prevention to a periodic spiral CT scan (the subjects are submitted to spiral CT scan yearly or every two years).

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