Interact CardioVasc Thorac Surg 2006;5:483-487. doi:10.1510/icvts.2006.130518
© 2006 European Association of Cardio-Thoracic Surgery
Best evidence topic - Thoracic general |
Does lung cancer screening with chest X-ray improve disease-free survival?
Ian Hunta,*,
Mayooran Sivaa,
Rachel Southonb and
Tom Treasurea
a Department of Cardiothoracic Surgery Centre, Guy's Hospital, St Thomas Street, London, SE1 7EH, UK
b Information Scientist, Royal College of Surgeons of England, Lincolns Inn Fields, London, UK
Received 10 February 2006;
received in revised form 31 March 2006;
accepted 4 April 2006
*Corresponding author. Tel.: +44 207 928 203; fax: +44 207 188 7703.
E-mail address: ian.hunt{at}gstt.nhs.uk (I. Hunt).
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Abstract
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A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was whether screening an asymptomatic person with a routine chest X-ray would detect lung cancer early and, most importantly, improve that person's disease-free survival from lung cancer. Altogether 136 papers were identified using the search below. Ten papers presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of the papers are tabulated. We conclude that despite methodological criticisms and concerns regarding biases inherent to screening studies, there is currently no evidence to support the use of chest X-ray to screen an asymptomatic person for lung cancer.
Key Words: Evidence-based medicine; Lung neoplasms; Mass screening; Tomography
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1. Introduction
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A best evidence topic was constructed according to a structured protocol. This protocol is fully described in the ICVTS [1].
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2. Clinical scenario
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You are a chest registrar seeing a 55-year-old patient in a rapid access out-patient clinic who has recently presented with cough and hemopytsis. He is a smoker and had these symptoms for just a few weeks before being sent for a chest X-ray. It shows a large lesion in the right upper zone. The patient suspects he has lung cancer, which he probably does. He wants to know why he could not have had a chest X-ray before he was sick to pick up his lung cancer.
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3. Three part question
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In (asymptomatic patients with risk factors for lung cancer) is the use of (Chest X-ray) of benefit in terms of (improved disease-free survival).
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4. Search strategy
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Medline 1966 – Feb 2006 and Embase 1980 – Feb 2006 using the Dialog Datastar interface [Lung-Neoplasms#.DE. OR Lung-Tumor#.DE. OR (Lung NEAR (Neoplasm$ OR Cancer$ OR Carcinoma$ OR Adenocarcinoma$ OR Angiosarcoma$ OR Chrondosarcoma$ OR Sarcoma$ OR Teratoma$ OR Lymphoma$ OR Blastoma$ OR Microcytic$ OR Carcinogenesis OR Tumor$ OR Tumour$ OR Metast$4)). TI,AB. OR NSCLC.TI,AB. OR SCLC.TI,AB.] AND [Mass-Screening.DE. OR Cancer-Screening.DE. OR (Screen$3 OR Case ADJ Finding OR Casefinding OR Case-Finding).TI,AB.] AND [Radiography-Toracic.DE. OR Mass-Chest-X-Ray.DE. OR Tomography-X-Ray.DE. OR Thorax-Radiography.DE. OR X-Ray.DE.] OR ((Chest OR Thoracic) NEAR (X ADJ Ray$ OR X-Ray$)).TI,AB.] limit to English. This search was repeated in Cochrane Central Register of Controlled Trials.
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5. Search outcome
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A total of 136 papers were found of which 10 were deemed to be relevant. Only Randomised Control Trials (RCTs) or reviews of RCTs were included. Several systematic reviews and Guidelines for screening were reviewed including the most recent and only meta-analysis on chest X-ray screening. The same group has subsequently updated its previous Cochrane review. The individual randomised trials are presented with the subsequent meta-analysis (Table 1).
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6. Comments
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The trials reviewed included only male current smokers over 40–45 years of age, and generally assessed more intense screening with chest X-ray±sputum cytology versus less intense chest X-ray screening. Typically the studies tended to show a higher incidence of lung cancer, a higher rate of surgical resection and a better survival in the more intensely screened groups. However, overall there appeared to be no significant reduction in mortality from lung cancer in the intense screening group compared to the less intense screened group. In fact, the subsequent meta-analysis [10] demonstrated that more frequent chest X-ray screening was associated with an 11% relative increase in mortality over less frequent screening. A non-statistically trend to reduced mortality from lung cancer was observed when screening with chest X-ray and sputum cytology was compared to chest X-ray alone (RR 0.88, 95% CI 0.74 to 1.03) [10,14].
The methodology of all the screening studies has been questioned. Criticisms include under-powering of the studies to detect a significant reduction in lung cancer mortality between the groups and adherence to study protocol. Others issues related to biases inherent to screening trials have been suggested to account for this apparent disparity. For example in the Mayo Lung project [6] rates of early tumours in the intense screening group were increased compared to the control group, without altering numbers of advanced cancers detected or mortality rates. This may reflect the fact that intense screening is diagnosing indolent tumours. This is referred to as an over-diagnosis bias, the detection of cancers that would not have become clinically apparent before that person died of other causes.
As well as overdiagnosis bias screening studies may be flawed by other biases; Lead-time bias is where early diagnosis in a screen-detected lung cancer patient falsely appears to prolong survival, despite the actual course of the disease ending in mortality, is the same whether you screen or not. Length bias refers to overestimation of survival duration among screening-detected lung cancer caused by the relative excess of slowly progressing cases. Screening over-represents less aggressive disease. Thus, a comparison between screen-detected lung cancer and others detected by the person developing symptoms or signs appears to overestimate benefit because the former consists of cases that were diagnosed earlier, progress more slowly, and may never become clinically relevant. Such biases all appear to inflate the survival of screen-detected cases
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7. Clinical bottom line
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The current evidence does not support the use of chest X-ray (with or without sputum cytology) as a screening test for lung cancer.
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Abstract
1. Introduction