The natural history of lung cancer estimated from the results of a randomized trial of screening

Screening for lung cancer

BACKGROUND

This is an updated version of the original review published in The Cochrane Library in 1999 and updated in 2004 and 2010. Population-based screening for lung cancer has not been adopted in the majority of countries. However it is not clear whether sputum examinations, chest radiography or newer methods such as computed tomography (CT) are effective in reducing mortality from lung cancer.

OBJECTIVES

To determine whether screening for lung cancer, using regular sputum examinations, chest radiography or CT scanning of the chest, reduces lung cancer mortality.

SEARCH METHODS

We searched electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 5), MEDLINE (1966 to 2012), PREMEDLINE and EMBASE (to 2012) and bibliographies. We handsearched the journal Lung Cancer (to 2000) and contacted experts in the field to identify published and unpublished trials.

SELECTION CRITERIA

Controlled trials of screening for lung cancer using sputum examinations, chest radiography or chest CT.

DATA COLLECTION AND ANALYSIS

We performed an intention-to-screen analysis. Where there was significant statistical heterogeneity, we reported risk ratios (RRs) using the random-effects model. For other outcomes we used the fixed-effect model.

MAIN RESULTS

We included nine trials in the review (eight randomised controlled studies and one controlled trial) with a total of 453,965 subjects. In one large study that included both smokers and non-smokers comparing annual chest x-ray screening with usual care there was no reduction in lung cancer mortality (RR 0.99, 95% CI 0.91 to 1.07). In a meta-analysis of studies comparing different frequencies of chest x-ray screening, frequent screening with chest x-rays was associated with an 11% relative increase in mortality from lung cancer compared with less frequent screening (RR 1.11, 95% CI 1.00 to 1.23); however several of the trials included in this meta-analysis had potential methodological weaknesses. We observed a non-statistically significant trend to reduced mortality from lung cancer when screening with chest x-ray and sputum cytology was compared with chest x-ray alone (RR 0.88, 95% CI 0.74 to 1.03). There was one large methodologically rigorous trial in high-risk smokers and ex-smokers (those aged 55 to 74 years with ≥ 30 pack-years of smoking and who quit ≤ 15 years prior to entry if ex-smokers) comparing annual low-dose CT screening with annual chest x-ray screening; in this study the relative risk of death from lung cancer was significantly reduced in the low-dose CT group (RR 0.80, 95% CI 0.70 to 0.92).

AUTHORS' CONCLUSIONS

The current evidence does not support screening for lung cancer with chest radiography or sputum cytology. Annual low-dose CT screening is associated with a reduction in lung cancer mortality in high-risk smokers but further data are required on the cost effectiveness of screening and the relative harms and benefits of screening across a range of different risk groups and settings.

[Gynecological screening or cervical screening? Conflicts between clinical and public health viewpoints]

The "gynecological screening" that is composed of complex gynecological examination including colposcopy and cytological examinations has traditionally been incorporated into the gynecological protocol and practice. Over the past few decades, unfortunately, this screening practice has entrenched in the mind both of the gynecological community and the general public. As a result, the government-supported, organized cervical screening program of the population has come to a standstill. In order to adjust the cervical screening practice to the international public health recommendations in which cytology is the only screening test applied, the authors decided to involve primary care nurses and health visitors in smear taking, and to refer those with abnormal findings to a gynecologist for further clinical examination.

Is our natural-history model of lung cancer wrong?

For screening to be successful in lung cancer, programmes need to identify a precursor of fatal disease that is highly treatable. This precursor is currently presumed to be early-stage lung cancer, and thus our current efforts in lung-cancer screening have focused on finding, and treating, early-stage lung cancer. In other words, our current natural-history model of lung cancer is based on the notion that for a period before a lung cancer becomes advanced and fatal, it is localised and treatable. Empirical findings emerging from studies of lung-cancer screening suggest this notion to be incorrect. These studies all suggest that early-stage histologically confirmed lung cancers identified by screening are not precursors of advanced or incurable disease. If true, these findings have potentially important implications for the development and assessment of new lung-cancer screening approaches.

Mean sojourn time and effectiveness of mortality reduction for lung cancer screening with computed tomography

This study aimed to estimate the mean sojourn time (MST) and sensitivity of asymptomatic lung cancer (ALC) detected by computed tomography (CT) or chest X-ray (CXR). Translation of early diagnosis into mortality reduction by 2 detection modalities and inter-screening interval was projected using a Markov model. On the basis of systematic literature review, data from 6 prospective CT screening studies were retrieved. The MST in association with the natural history of lung cancer depicted by a 3-state Markov model was estimated with a Bayesian approach. To project mortality reduction attributed to screening, the model was further extended to 5 health states for the inclusion of prognostic part. The analysis was run with a 10-year time horizon of follow-up, mimicking the Dutch-Belgian randomized lung cancer screening trial (NELSON). Screening for lung cancer with CT had high sensitivity (median: 97%) and may advance 1 year earlier than CXR in detecting ALC. By simulating the scenario similar to NELSON study, CT screen may gain an extra of 0.019 year of life expectancy per person, yields 15% mortality reduction (relative risk (RR): 0.85, 95% confidence interval [95%CI: (0.58-1.01)]. Approximate 23% [RR: 0.77, 95%CI: (0.43-0.98)] mortality reduction would be achieved by annual CT screening program. The mortality findings in conjunction with higher sensitivity and shorter MST estimate given data on prevalent and incident (2nd) screen may provide a tentative evidence, suggesting that annual CT screening may be required in order to be effective in reducing mortality before the results of randomized controlled studies available.

Estimation of mean sojourn time for lung cancer by chest X-ray screening with a Bayesian approach

Very few studies, particularly from oriental population, reported the progression of lung cancer from asymptomatic to symptomatic phase. The present study aimed to estimate mean sojourn time (MST) of lung cancer, an average duration period in which tumour can be asymptotically detected by chest X-ray (CXR), taking into account gender, smoking and histological type. Based on institutional cancer registry for lung cancer patients with prior non-diagnostic CXR (n=221), data were collected on demographic features, histology type, survival status, history of smoking, and asymptomatic or symptomatic status in light of chief complaint at diagnosis retrieved from medical records. The MST for the natural history of lung cancer underpinning a three-state Markov model was estimated with a Bayesian approach. The estimated MST for lung cancer was 5.51 months (95% credible interval: 4.04-7.12). Small cell lung carcinoma was even statistically significantly shorter MST than non-small cell lung carcinoma (3.01 (3-3.98) months vs. 6.07 (4.44-8.25) months). In parallel with literatures reporting tumour growth rate related to CXR and computed tomography (CT), the shorter mean sojourn time by using CXR estimated in our study strongly suggests that CT screening may be more effective in early detection of lung cancer in population-based screening.

[Screening for early detection of lung cancer: conflict between clinical and public health viewpoints]

In Hungary, lung cancer, gradually increasing among women, is the leading cause of cancer mortality. The screening, using chest x-ray and sputum cytology as screening tool, does not reduce the mortality from lung cancer, therefore, screening for lung cancer is not recommended. The low-dose spiral CT is a sensitive and promising method, however, its specificity is far from being ideal. The results of the on-going RCTs are expected in a few years time, and so far it is not applicable for routine screening. In this country, the one-third of lung cancer cases are detected by the routine chest x-ray for tuberculosis, obligatory by law, and most of the detected cases are still resectable, but this does not have any influence on the mortality. According to our view, the detection of the lung cancer, particularly in those at high risk, is a by-product of periodic chest x-ray aiming at early detection of tuberculosis, however, mass screening for lung cancer as public health measure is not recommended. For the time being, the implementation of tobacco control measures is the only way to reduce the risk of lung cancer in the long run.

Computed tomography screening for lung cancer in Hodgkin's lymphoma survivors: decision analysis and cost-effectiveness analysis

BACKGROUND

Hodgkin's lymphoma patients have an elevated risk of developing lung cancer and may be targeted for lung cancer screening. We used a decision-analytic model to estimate the potential clinical benefits and cost-effectiveness of computed tomography (CT) screening for lung cancer in Hodgkin's lymphoma survivors.

MATERIALS AND METHODS

We developed a Markov decision-analytic model to compare annual low-dose CT screening versus no screening in a hypothetical cohort of patients diagnosed with stage IA-IIB Hodgkin's lymphoma at age 25, with screening starting 5 years after initial diagnosis. We derived model parameters from published studies and the Surveillance, Epidemiology and End Results (SEER) Program, and assumed that stage-shift produces a survival benefit.

RESULTS

Annual CT screening increased survival by 0.64 years for smokers and 0.16 years for non-smokers. The corresponding benefits in quality-adjusted survival were 0.58 quality-adjusted life-years (QALYs) for smokers and 0.14 QALYs for non-smokers. The incremental cost-effectiveness ratios for annual CT screening compared with no screening were $34 100/QALY for smokers and $125 400/QALY for non-smokers.

CONCLUSIONS

Our analysis suggests that if early promising results for lung cancer screening hold, CT screening for lung cancer may increase survival and quality-adjusted survival among Hodgkin's lymphoma survivors, with a benefit and incremental cost-effectiveness ratio for smokers comparable to that of other recommended cancer screening strategies.

Cost Effectiveness of Chest Computed Tomography After Lung Cancer Resection: A Decision Analysis Model

BACKGROUND

Postoperative surveillance with chest computed tomography (CT) is often performed in patients who have undergone resection of non-small cell lung cancer (NSCLC), despite lack of supporting data. This study involves the creation of a decision analysis model to predict the cost effectiveness of postoperative surveillance CT.

METHODS

A decision analysis model was created in which a hypothetical cohort of patients underwent annual chest CT after resection of a stage IA NSCLC. The incidence of second primary lung cancer (SPLC), sensitivity and specificity of CT, as well as survival after resection of initial primary and SPLC were derived from published literature. The cost of CT and other procedures prompted by a positive finding on CT was calculated from Medicare reimbursement schedules. Cost effectiveness was defined as a cost of less than 60,000 dollars per quality-adjusted life-year gained in the cohort under surveillance compared with controls under no surveillance.

RESULTS

In the initial (base case) analysis, the cost of surveillance CT was 47,676 dollars per quality-adjusted life-year gained, implying cost effectiveness. However, factors that rendered surveillance CT cost ineffective were (1) age at entry into the surveillance program greater than 65 years, (2) cost of CT greater than 700 dollars, (3) incidence of SPLC of less than 1.6% per patient per year of follow-up, and (4) a false positive rate of surveillance CT greater than 14%.

CONCLUSIONS

Surveillance with postoperative CT may be a cost-effective intervention to detect SPLC in selected patients with previously resected stage IA NSCLC.

Screening for lung cancer

BACKGROUND

While population based screening for lung cancer has not been adopted by most countries, it is not clear whether sputum examinations, chest radiography or newer methods such as computed tomography are effective in reducing mortality from lung cancer.

OBJECTIVES

To determine whether screening for lung cancer using regular sputum examinations or chest radiography or CT chest reduces lung cancer mortality.

SEARCH STRATEGY

Electronic databases (the Cochrane Central Register of Controlled Trials, MEDLINE, PREMEDLINE and EMBASE; 1966 to July 2000) ), bibliographies, hand searching of a journal and discussion with experts were used to identify published and unpublished trials.

SELECTION CRITERIA

Controlled trials of screening for lung cancer using sputum examinations, chest radiography or CT chest.

DATA COLLECTION AND ANALYSIS

Intention to screen analysis was performed. Where there was significant statistical heterogeneity relative risks were reported using the random effects model, but for other outcomes the fixed effect model was used.

MAIN RESULTS

Seven trials were included (6 randomised controlled studies and 1 non-randomised controlled trial) with a total of 245,610 subjects. There were no studies with an unscreened control group. Frequent screening with chest x-rays was associated with an 11% relative increase in mortality from lung cancer compared with less frequent screening (RR 1.11, CI: 1.00-1.23). A non statistically significant trend was observed to reduced mortality from lung cancer when screening with chest x-ray and sputum cytology was compared with chest x-ray alone (RR 0.88, CI:0.74-1.03). Several of the included studies had potential methodological weaknesses. There were no controlled studies of spiral CT.

REVIEWER'S CONCLUSIONS

The current evidence does not support screening for lung cancer with chest radiography or sputum cytology. Frequent chest x-ray screening might be harmful. Further, methodologically rigorous trials are required.

Lung cancer screening with helical computed tomography in older adult smokers: a decision and cost-effectiveness analysis

CONTEXT

Encouraged by direct-to-consumer marketing, smokers and their physicians are contemplating lung cancer screening with a promising but unproven imaging procedure, helical computed tomography (CT).

OBJECTIVE

To estimate the potential benefits, harms, and cost-effectiveness of lung cancer screening with helical CT in various efficacy scenarios.

DESIGN, SETTING, AND POPULATION

Using a computer-simulated model, we compared annual helical CT screening to no screening for hypothetical cohorts of 100 000 current, quitting, and former heavy smokers, aged 60 years, of whom 55% were men. We simulated efficacy by changing the clinical stage distribution of lung cancers so that the screened group would have fewer advanced-stage cancers and more localized-stage cancers than the nonscreened group (ie, a stage shift). Our model incorporated known biases in screening programs such as lead time, length, and overdiagnosis bias.

MAIN OUTCOME MEASURES

We measured the benefits of screening by comparing the absolute and relative difference in lung cancer-specific deaths. We measured harms by the number of false-positive invasive tests or surgeries per 100 000 and incremental cost-effectiveness in US dollars per quality-adjusted life-year (QALY) gained.

RESULTS

Over a 20-year period, assuming a 50% stage shift, the current heavy smoker cohort had 553 fewer lung cancer deaths (13% lung cancer-specific mortality reduction) and 1186 false-positive invasive procedures per 100 000 persons. The incremental cost-effectiveness for current smokers was $116 300 per QALY gained. For quitting and former smokers, the incremental cost-effectiveness was $558 600 and $2 322 700 per QALY gained, respectively. Other than the degree of stage shift, the most influential parameters were adherence to screening, degree of length or overdiagnosis bias in the first year of screening, quality of life of persons with screen-detected localized lung cancers, cost of helical CT, and anxiety about indeterminate nodule diagnoses. In 1-way sensitivity analyses, none of these parameters was sufficient to make screening highly cost-effective for any of the cohorts. In multiway sensitivity analyses, a program screening current smokers was $42 500 per QALY gained if extremely favorable estimates were used for all of the influential parameters simultaneously.

CONCLUSION

Even if efficacy is eventually proven, screening must overcome multiple additional barriers to be highly cost-effective. Given the current uncertainty of benefits, the harms from invasive testing, and the high costs associated with screening, direct-to-consumer marketing of helical CT is not advisable.

Epidemiology of lung cancer

This review article presents lung cancer epidemiology, describing main epidemiologic characteristics including epidemiological situation in cancer incidence, mortality and survival in Europe in comparison with situation in the Czech Republic. Influence of environmental and life style risk factors like smoking, passive smoking, risk factors of work environment, ionizing radiation, air pollution, nutrition and genetic and hormonal factors are discussed.

Lung cancer screening by spiral CT. What is the optimal target population for screening trials?

The purpose of this document is to provide recommendations for the selection of the optimal target population for lung cancer screening trials with Spiral Computer Tomography based on an analysis of risk factors and high-risk populations. Our recommendations are to include current or ex-smokers (<5 years) with a smoking history of at least 30 years and an average consumption of at least 20 cigarettes a day. When these selection criteria are applied there is no need for a lower age cut-off. Elderly people can be included as long as their life expectancy is more than 10 years. Participants should be fit enough to undergo thoracic surgery. They may have a history of previous cancer, provided that the cancer has been curatively treated at least 5 years ago without evidence of relapse, except for breast cancer, melanoma and hypernephroma. People with an inability to lie flat, who are unable to hold their breath for 20 s, with a body weight above 140 kg, a chest CT scan within 1 year before enrolment or a previous pneumonectomy should not be invited. The inadequacy of the unit 'Pack-Years' (PY) to estimate the individual lung cancer risk is recognised, and future initiatives to develop an appropriate lung cancer risk model are encouraged.

Screening for lung cancer

BACKGROUND

The effectiveness of screening for lung cancer with chest radiography, sputum cytology or spiral CT has not been established.

OBJECTIVES

To determine whether screening for lung cancer using regular sputum examinations or chest radiography or CT chest reduces lung cancer mortality.

SEARCH STRATEGY

Electronic databases, bibliographies, hand searching of a journal and discussion with experts were used to identify published and unpublished trials.

SELECTION CRITERIA

Controlled trials of screening for lung cancer using sputum examinations, chest radiography or CT chest.

DATA COLLECTION AND ANALYSIS

Intention to screen analysis was performed. Where there was significant statistical heterogeneity relative risks were reported using the random effect model, but for other outcomes the fixed effect model was used.

MAIN RESULTS

Seven trials were included (6 randomised controlled studies and 1 non-randomised controlled trial) with a total of 245,610 subjects. There were no studies with an unscreened control group. Frequent screening with chest x-rays was associated with an 11% relative increase in mortality from lung cancer compared with less frequent screening (RR 1.11, CI: 1.00-1.23). A non statistically significant trend was observed to reduced mortality from lung cancer when screening with chest x-ray and sputum cytology was compared with chest x-ray alone (RR 0.88, CI:0.74-1.03). Several of the included studies had potential methodological weaknesses. There were no controlled studies of spiral CT.

REVIEWER'S CONCLUSIONS

The current evidence does not support screening for lung cancer with chest radiography or sputum cytology. Frequent chest x-ray screening might be harmful. Further, methodologically rigorous trials are required.

Lung cancer screening: improved survival but no reduction in deaths--the role of "overdiagnosis"

BACKGROUND

Randomized controlled trials (RCTs) of lung cancer screening consistently show an excess number of cancer cases and longer survival in screened groups, but no difference in mortality between screened and control populations.

METHODS

The current study reviewed the various types of biases that confuse comparisons based on intermediate endpoints such as stage distribution and survival and the reasons for basing evaluations in RCTs of screening for early cancers on mortality from a specific cancer.

RESULTS

Four RCTs all showed improved stage of disease and survival in screened subjects, but there was no difference in mortality between screened and unscreened populations. The possible explanations for the higher incidence are chance (failed randomization) or "overdiagnosis" (detection of cases by screening that otherwise would never have surfaced). Analysis of the trial results confirmed that chance alone was a very unlikely explanation. Evidence suggests that some overdiagnosis of lung cancer is likely in screened subjects. This is a consistent observation in all other programs of screening for early cancers (breast, prostate, and neuroblastoma).

CONCLUSIONS

Overdiagnosis of cancer cases resulting from the screening process itself will give rise to excess cases of disease, and may, at least in part, explain the observations in the randomized trials.

Early detection in lung cancer. Case finding and screening

There is general agreement that the most effective approach to lung cancer is primary prevention--stop smoking. Richards has proposed the MVROCST--the Monosyllabic Verbal Response Office Cancer Screening Test: "Do you smoke?" If "yes," intervene. If "no," move on. Ample evidence exists that a clear message from a physician to a patient about the importance of stopping smoking makes a difference. In contrast to the maze of arguments and data on early detection, this is something that each physician clearly can and should do. A reduced risk for lung cancer may begin as early as 5 years after cessation of cigarette use. Huuskonen has proposed conceptualizing screening as a coordinated intervention with the goal of identifying populations at risk and working to modify that risk. Primary prevention should be central to any efforts to reduce mortality from lung cancer, and attention to this area needs to increase despite the difficulties and frustration. Despite declining percentages of smokers in the population as a whole, it is estimated that more than 3000 teenagers become regular smokers each day in the United States. In this environment, the question of whether to recommend a CXR or sputum for early detection is not going to disappear in the near future. The NCI has recognized the persistent and important nature of this debate and is currently funding the Prostate, Lung, Colon and Ovary Cancer Screening Trial. This is a large and powerful randomized study of men and women aged 60 to 74. The lung cancer arm is designed to look at the usefulness of a yearly CXR intervention in reducing cancer-specific mortality. The overall power of the study (based on national mortality data) is 0.99 for a 15% reduction in lung cancer mortality and 0.89 for a 10% reduction, with differentially better sensitivity in men than women. The study is currently in progress at multiple sites and will be completed over the next 12 to 14 years. In the meantime, what is the right approach? It is useful in considering this question to return to the concepts of early detection, screening, and case finding. 1. Early detection in lung cancer remains a concept of uncertain applicability because of the unknowns and variability in the natural history of the disease. The available, accessible, and acceptable detection tools appear to be inadequate by current evidence. This is not a static field, however, and new work in the area of biomarkers carries promise for significantly more sensitive and specific techniques. Tockman and colleagues conclude that early detection is conceptually sound, although not currently practical, and further research may expand the role of intervention. In the end, a judgement on early detection in lung cancer must be linked to the proposed setting--screening or case finding. 2. Screening, defined as the application of a test to the general population to define disease risk further with the implied benefit of improved treatment and outcome, cannot be recommended for lung cancer. This is the perspective of the major organizations cited previously, and it is based on admittedly imperfect but nonetheless convincing data. 3. Case finding, the situation of the patient who seeks care and is available for informed discussion and negotiation on possible testing, is a potentially different situation.(ABSTRACT TRUNCATED)

Cancer survival and the duration of symptoms. An analysis of possible forms of the risk function. ISDS II Project Investigators

The time interval between onset of symptoms and the diagnosis of cancer [symptom to diagnosis interval (SDI), or duration of symptoms] is a highly complex variable reflecting patient behaviour, the clinical course, the functioning of the health system and tumour biology. In order to assess possible forms of the risk function of SDI upon cancer survival whilst taking into account the effects of age, sex, tumour site and stage at diagnosis, 1887 symptomatic cases of lung, breast, stomach, colon, rectal, bladder cancer and lymphomas registered in the Tumour Registry of the Hospital del Mar (Barcelona) were analysed by means of survival curves and Cox proportional hazards regression. Subjects (mean age 64 years) were followed for a median length of 15 months after diagnosis (follow-up rate 93.5%). SDI showed a weak relationship with tumour stage at diagnosis and with survival: out of the seven sites studied, only in breast cancer was tumour extension at diagnosis significantly influenced by duration of symptoms, and only lung and rectal cancers showed a detectable form of the risk function of SDI upon survival; neither was linear, and for rectal cancer the relationship was complexly related with tumour stage. Hence, results show that forms of the risk function of duration of symptoms on cancer survival are specific to tumour sites, and that the interval should not be represented as a linear, continuous term. Studies analysing more complex sets of factors, processes and forms of the SDI function are needed.