Extended lung cancer incidence follow-up in the Mayo Lung Project and overdiagnosis

Screening and early detection efforts in lung cancer

Lung cancer is the leading cause of cancer-related death in the United States. Since publication of results from the National Lung Screening Trial, several professional organizations, including the US Preventive Services Task Force, have published guidelines recommending low-dose computed tomography for screening in asymptomatic, high-risk individuals. The benefits of screening include detection of cancer at an early stage when a definitive cure is possible, but the risks include overdiagnosis, false-positive results, psychological distress, and radiation exposure. The current review covers the scope of low-dose computed tomography screening, potential risks, costs, and future directions in the efforts for early detection of lung cancer.

Lung cancer screening: advantages, controversies, and applications

BACKGROUND

Lung cancer is the leading cause of cancer death in the United States. Results from the National Lung Screening Trial (NLST) have shown that low-dose computed tomography (CT) is capable of detecting lung neoplasms in individuals at high risk. However, whether it is advantageous to perform lung cancer screening on these patients is a significant concern, as are the potential adverse outcomes from screening.

METHODS

A review of several randomized clinical trials, focusing on the NLST, was undertaken. Adverse outcomes and costs related to lung cancer screening were also examined.

RESULTS

Lung cancer screening using low-dose CT in high-risk individuals reduced lung cancer deaths by more than 20% when compared with those screened by chest radiography. False-positive results were seen in both groups, but the number of adverse events from the screening test and subsequent diagnostic procedures was low.

CONCLUSIONS

Lung cancer screening is controversial, but the NLST has demonstrated that such testing may reduce lung cancer deaths in high-risk individuals when performed with low-dose CT rather than chest radiography. Guidelines should be established to not only help identify an appropriate screening population, but also develop standards for radiological testing.

Screening for lung cancer

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the current data about low-dose computed tomography (LD-CT) lung cancer screening.

RECENT FINDINGS

The National Lung Screening Trial (NLST) was the first study that provided statistical evidence that LD-CT screening for lung cancer significantly reduces lung cancer mortality by 20%. Three statistically underpowered European trials could not confirm the positive effect of LD-CT screening on lung cancer mortality. Major obstacles in lung cancer screening are overdiagnosis and the large number of false-positive results. In the NLST, more than 24% of the screens were positive, most of which (96.4%) proved to be benign in nature. Optimized protocols for the workup of detected nodules may help to reduce the number of false-positive screens.

SUMMARY

Currently, the NLST is the only sufficiently powered trial to report a lower mortality rate with LD-CT screening. Long-term follow-up data are still anticipated on the European screening trials. Furthermore, data on the extent of the potential dangers of LD-CT screening, such as overdiagnosis, false-positive results, and the effect of cumulative radiation dose, have yet to be investigated thoroughly.

Issues with implementing a high-quality lung cancer screening program

After a comprehensive review of the evidence, the United States Preventive Services Task Force recently endorsed screening with low-dose computed tomography as an early detection approach that has the potential to significantly reduce deaths due to lung cancer. Prudent implementation of lung cancer screening as a high-quality preventive health service is a complex challenge. The clinical evaluation and management of high-risk cohorts in the absence of symptoms mandates an approach that differs significantly from that of symptom-detected lung cancer. As with other cancer screenings, it is essential to provide to informed at-risk individuals a safe, high-quality, cost-effective, and accessible service. In this review, the components of a successful screening program are discussed as we begin to disseminate lung cancer screening as a national resource to improve outcomes with this lethal cancer. This information about lung cancer screening will assist clinicians with communications about the potential benefits and harms of this service for high-risk individuals considering participation in the screening process.

Symptom lead time distribution in lung cancer: natural history and prospects for early diagnosis

BACKGROUND

Before their diagnosis, patients with cancer present in primary care more frequently than do matched controls. This has raised hopes that earlier investigation in primary care could lead to earlier stage at diagnosis.

METHODS

We re-analysed primary care symptom data collected from 247 lung cancer cases and 1235 matched controls in Devon, UK. We identified the most sensitive and specific definition of symptoms, and estimated its incidence in cases and controls prior to diagnosis. We estimated the symptom lead time (SLT) distribution (the time between symptoms attributable to cancer and diagnosis), taking account of the investigations already carried out in primary care. The impact of route of diagnosis on stage at diagnosis was also examined.

RESULTS

Symptom incidence in cases was higher than in controls 2 years before diagnosis, accelerating markedly in the last 6 months. The median SLT was under 3 months, with mean 5.3 months [95% credible interval (CrI) 4.5-6.1] and did not differ by stage at diagnosis. An earlier stage at diagnosis was observed in patients identified through chest X-ray originated in primary care.

CONCLUSIONS

Most symptoms preceded clinical diagnosis by only a few months. Symptom-based investigation would lengthen lead times and result in earlier stage at diagnosis in a small proportion of cases, but would be far less effective than standard screening targeted at smokers.

[Overdiagnosis in cancer screening]

In screening programs, overdiagnosis is defined as the detection of a disease that would have gone undetected without screening when that disease would not have resulted in morbimortality and was treated unnecessarily. Overdiagnosis is a bias inherent in screening and an undesired effect of secondary prevention and improved sensitivity of diagnostic techniques. It is difficult to discriminate a priori between clinically relevant diagnoses and those in which treatment is unnecessary. To minimize the effects of overdiagnosis, screening should be done in patients at risk.

CT lung cancer screening: where are we heading to?

SUMMARY 

Lung cancer screening has been the subject of controversies since the 1970s. After failure of chest x-ray and sputum cytology examination to decrease lung cancer mortality, there was a 15-year period of disillusion. Low-dose CT scan of the thorax provided a renewal of interest with prospective studies followed by randomized trials of which four have been published. Only one, the NLST trial involving 53,000 participants is positive with a 20% reduction in lung cancer specific mortality rate. The European studies are by far smaller, the largest being the Nelson study with 15,000 participants. There are some shortcomings and biases that must be known and well explained to the future participants to a lung cancer screening program. The cost/benefit ratio remains to be better analyzed.

Lung Cancer Screening With Low-Dose CT: Its Effect on Smoking Behavior

Lung cancer screening provides an opportunity for smoking cessation interventions. A review of the literature found that smokers who participated in lung cancer screening had a higher smoking cessation rate compared with smokers in the general population. However, the randomized controlled trials included in the review did not identify any difference in smoking cessation rates between the individuals who had a CT scan to screen for lung cancer and unscreened control groups. Multiple studies observed participants for lengths of time ranging from 1 to 36 months and concluded that individuals who received abnormal CT results had a higher smoking cessation rate compared with participants with normal CT results. A single study that observed participants for 6 years initially found similar increased cessation rates among those with abnormal CT results, but at the conclusion of the study the difference in cessation rates had dissipated. Lung cancer screening produces a teachable moment when individuals may be more receptive to smoking cessation interventions. Advanced practitioners should take an active role in promoting smoking cessation interventions and fostering this teachable moment created by lung cancer screening.

Addressing overdiagnosis and overtreatment in cancer: a prescription for change

A vast range of disorders--from indolent to fast-growing lesions--are labelled as cancer. Therefore, we believe that several changes should be made to the approach to cancer screening and care, such as use of new terminology for indolent and precancerous disorders. We propose the term indolent lesion of epithelial origin, or IDLE, for those lesions (currently labelled as cancers) and their precursors that are unlikely to cause harm if they are left untreated. Furthermore, precursors of cancer or high-risk disorders should not have the term cancer in them. The rationale for this change in approach is that indolent lesions with low malignant potential are common, and screening brings indolent lesions and their precursors to clinical attention, which leads to overdiagnosis and, if unrecognised, possible overtreatment. To minimise that potential, new strategies should be adopted to better define and manage IDLEs. Screening guidelines should be revised to lower the chance of detection of minimal-risk IDLEs and inconsequential cancers with the same energy traditionally used to increase the sensitivity of screening tests. Changing the terminology for some of the lesions currently referred to as cancer will allow physicians to shift medicolegal notions and perceived risk to reflect the evolving understanding of biology, be more judicious about when a biopsy should be done, and organise studies and registries that offer observation or less invasive approaches for indolent disease. Emphasis on avoidance of harm while assuring benefit will improve screening and treatment of patients and will be equally effective in the prevention of death from cancer.

Lung cancer screening guidelines: common ground and differences

Lung cancer accounts for almost one-third of all cancer related deaths. Lung cancer risk persists even after smoking cessation and so many lung cancers now are diagnosed in former smokers. Five-year survival of lung cancer has marginally improved over decades and significantly lags behind that of colon, breast and prostate cancer. Over the past one decade, lung cancer screening trials have shown promising results. Results from National Lung Cancer Screening Trial (NLST), have shown a significant 20% reduction in mortality with annual low dose computed tomography (LDCT) screening. Based on these results, annual LDCT testing has been recommended for lung cancer screening in high risk population. However, development and acceptance of lung cancer screening as a public health policy is still in the nascent stages. Major concerns relate to risk of radiation, overdiagnosis bias, proportion of false positives and cost benefit analysis. This article reviews the literature pertaining to lung cancer screening guidelines and above mentioned concerns.

Overdiagnosis in low-dose computed tomography screening for lung cancer

IMPORTANCE

Screening for lung cancer has the potential to reduce mortality, but in addition to detecting aggressive tumors, screening will also detect indolent tumors that otherwise may not cause clinical symptoms. These overdiagnosis cases represent an important potential harm of screening because they incur additional cost, anxiety, and morbidity associated with cancer treatment.

OBJECTIVE

To estimate overdiagnosis in the National Lung Screening Trial (NLST).

DESIGN, SETTING, AND PARTICIPANTS

We used data from the NLST, a randomized trial comparing screening using low-dose computed tomography (LDCT) vs chest radiography (CXR) among 53 452 persons at high risk for lung cancer observed for 6.4 years, to estimate the excess number of lung cancers in the LDCT arm of the NLST compared with the CXR arm.

MAIN OUTCOMES AND MEASURES

We calculated 2 measures of overdiagnosis: the probability that a lung cancer detected by screening with LDCT is an overdiagnosis (PS), defined as the excess lung cancers detected by LDCT divided by all lung cancers detected by screening in the LDCT arm; and the number of cases that were considered overdiagnosis relative to the number of persons needed to screen to prevent 1 death from lung cancer.

RESULTS

During follow-up, 1089 lung cancers were reported in the LDCT arm and 969 in the CXR arm of the NLST. The probability is 18.5% (95% CI, 5.4%-30.6%) that any lung cancer detected by screening with LDCT was an overdiagnosis, 22.5% (95% CI, 9.7%-34.3%) that a non-small cell lung cancer detected by LDCT was an overdiagnosis, and 78.9% (95% CI, 62.2%-93.5%) that a bronchioalveolar lung cancer detected by LDCT was an overdiagnosis. The number of cases of overdiagnosis found among the 320 participants who would need to be screened in the NLST to prevent 1 death from lung cancer was 1.38.

CONCLUSIONS AND RELEVANCE

More than 18% of all lung cancers detected by LDCT in the NLST seem to be indolent, and overdiagnosis should be considered when describing the risks of LDCT screening for lung cancer.

Current status of lung cancer screening

Low-dose CT (LDCT) is effective in the early detection of lung cancer, providing higher resectability and long-term survival rates. The National Lung Screening Trial shows a statistically significant mortality reduction in LDCT compared with chest radiography. The efficacy and safety of annual LDCT screening in heavy smokers must be explored, and the magnitude of benefit compared with the cost of large-scale screening. Trials in Europe have different study designs and an observational arm. Strategies to reduce lung cancer mortality should combine early detection with primary prevention and innovative biologic approaches.

[Advance of lung cancer screening with low-dose spiral CT]

Lung cancer has become the leading cause of cancer mortality globally, and 5-year survival rate is very poor. Screening and early detection are vital to improve survival and decrease mortality of lung cancer. In recent 20 years, low-dose spiral CT (LDCT) screening has become a research focus in this area. Randomized controlled trials have confirmed that LDCT can decrease lung cancer mortality. However, there are still some problems of LDCT. In this paper, we summarized the controversy that whether low-dose helical CT screening can reduce lung cancer mortality or not before its effectiveness was been confirmed, the results and problems in the randomized controlled trials and gave a prospect of low-dose helical CT screening's future application.

Radiation risk from CT: implications for cancer screening

OBJECTIVE

The cancer risks associated with patient exposure to radiation from medical imaging have become a major topic of debate. The higher doses necessary for technologies such as CT and the increasing utilization of these technologies further increase medical radiation exposure to the population. Furthermore, the use of CT for population-based cancer screening continues to be explored for common malignancies such as lung cancer and colorectal cancer. Given the known carcinogenic effects of ionizing radiation, this warrants evaluation of the balance between the benefit of early cancer detection and the risk of screening-induced malignancy.

CONCLUSION

This report provides a brief review of the process of radiation carcino-genesis and the literature evaluating the risk of malignancy from CT, with a focus on the risks and benefits of CT for cancer screening. The available data suggest a small but real risk of radiation-induced malignancy from CT that could become significant at the population level with widespread use of CT-based screening. However, a growing body of literature suggests that the benefits of CT screening for lung cancer in high-risk patients and CT colonography for colorectal cancer may significantly outweigh the radiation risk. Future studies evaluating the benefits of CT screening should continue to consider potential radiation risks.

Quantification of harms in cancer screening trials: literature review

OBJECTIVES

To assess how often harm is quantified in randomised trials of cancer screening.

DESIGN

Two authors independently extracted data on harms from randomised cancer screening trials. Binary outcomes were described as proportions and continuous outcomes with medians and interquartile ranges.

DATA SOURCES

For cancer screening previously assessed in a Cochrane review, we identified trials from their reference lists and updated the search in CENTRAL. For cancer screening not assessed in a Cochrane review, we searched CENTRAL, Medline, and Embase.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised trials that assessed the efficacy of cancer screening for reducing incidence of cancer, cancer specific mortality, and/or all cause mortality.

DATA EXTRACTION

Two reviewers independently assessed articles for eligibility. Two reviewers, who were blinded to the identity of the study's authors, assessed whether absolute numbers or incidence rates of outcomes related to harm were provided separately for the screening and control groups. The outcomes were false positive findings, overdiagnosis, negative psychosocial consequences, somatic complications, invasive follow-up procedures, all cause mortality, and withdrawals because of adverse events.

RESULTS

Out of 4590 articles assessed, 198 (57 trials, 10 screening technologies) matched the inclusion criteria. False positive findings were quantified in two of 57 trials (4%, 95% confidence interval 0% to 12%), overdiagnosis in four (7%, 2% to 18%), negative psychosocial consequences in five (9%, 3% to 20%), somatic complications in 11 (19%, 10% to 32%), use of invasive follow-up procedures in 27 (47%, 34% to 61%), all cause mortality in 34 (60%, 46% to 72%), and withdrawals because of adverse effects in one trial (2%, 0% to 11%). The median percentage of space in the results section that reported harms was 12% (interquartile range 2-19%).

CONCLUSIONS

Cancer screening trials seldom quantify the harms of screening. Of the 57 cancer screening trials examined, the most important harms of screening--overdiagnosis and false positive findings--were quantified in only 7% and 4%, respectively.

Screening for lung cancer: Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines

BACKGROUND

Lung cancer is by far the major cause of cancer deaths largely because in the majority of patients it is at an advanced stage at the time it is discovered, when curative treatment is no longer feasible. This article examines the data regarding the ability of screening to decrease the number of lung cancer deaths.

METHODS

A systematic review was conducted of controlled studies that address the effectiveness of methods of screening for lung cancer.

RESULTS

Several large randomized controlled trials (RCTs), including a recent one, have demonstrated that screening for lung cancer using a chest radiograph does not reduce the number of deaths from lung cancer. One large RCT involving low-dose CT (LDCT) screening demonstrated a significant reduction in lung cancer deaths, with few harms to individuals at elevated risk when done in the context of a structured program of selection, screening, evaluation, and management of the relatively high number of benign abnormalities. Whether other RCTs involving LDCT screening are consistent is unclear because data are limited or not yet mature.

CONCLUSIONS

Screening is a complex interplay of selection (a population with sufficient risk and few serious comorbidities), the value of the screening test, the interval between screening tests, the availability of effective treatment, the risk of complications or harms as a result of screening, and the degree with which the screened individuals comply with screening and treatment recommendations. Screening with LDCT of appropriate individuals in the context of a structured process is associated with a significant reduction in the number of lung cancer deaths in the screened population. Given the complex interplay of factors inherent in screening, many questions remain on how to effectively implement screening on a broader scale.

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.

Squamous dysplasia--the precursor lesion for esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) accounts for 80% of all esophageal cancers worldwide, and esophageal squamous dysplasia (ESD) is the only histopathology that predicts the development of ESCC. The prevalence of ESD parallels rates of invasive ESCC and is typically found in 25% or more of adults above the age of 35 years in populations in north central China, where risk for ESCC is among the highest in the world. Results of chemoprevention and early detection studies to prevent progression of ESD suggest that these approaches, coupled with emerging endoscopic therapies, offer promise for the prevention of esophageal cancer mortality in high-risk populations. Future research on ESD and ESCC should focus on finding additional modifiable risk factors and on identifying biomarkers to incorporate into early detection strategies.

Principles, effectiveness and caveats in screening for cancer

BACKGROUND

Cancer screening has the potential to prevent or reduce incidence and mortality of the target disease, but may also be harmful and have unwanted side-effects.

METHODS

This review explains the basic principles of cancer screening, common pitfalls in evaluation of effectiveness and harms of screening, and summarizes the evidence for effects and harms of the most commonly used cancer screening tools.

RESULTS

Cancer screening has either been established or is considered for breast, lung, prostate, cervical and colorectal cancer. In contrast, screening for gastrointestinal malignancies outside the large bowel is not generally accepted, available or implemented. Oesophageal and gastric carcinoma, and hepatocellular carcinoma, may be subject to screening in certain risk populations, but currently not for population screening based on available technology. Screening for colorectal cancer and cervical cancer by endoscopy and cytology respectively can decrease incidence of the target disease, whereas screening tools for lung, prostate and breast cancer detect early-stage invasive disease and thus do not decrease disease incidence. Overdiagnosis (detection of cancers that will not have become clinically apparent in the absence of screening) is a challenge in lung, prostate and breast cancer screening. The improvement of quality of clinical practice following the introduction of cancer screening programmes is an appreciated 'side-effect', but it is important to disentangle the effect of screening on cancer incidence and mortality from that of quality improvement of clinical services. As new, powerful screening tests emerge-particularly in molecular and genetic fields, but also in radiology and other clinical diagnostics-the basic requirements for screening evaluation and implementation must be borne in mind.

CONCLUSION

Cancer screening has been established for several cancer forms in Europe. The potential for incidence and mortality reduction is good, but harms do exist that need to be addressed, and communicated to the public.

Lung cancer screening with low-dose computed tomography after the National Lung Screening Trial. The debate is still open

The aim of this article is to highlight some concerns regarding lung cancer screening with CT through a thorough analysis of scientific literature. The publication of the National Lung Screening Trial in 2011 has revealed that CT screening of smokers and ex-smokers in three annual rounds reduces lung cancer mortality a 20% when compared with thorax x-ray screening. The first limitation of this screening modality is its lack of downstaging in successive screening rounds compared with the initial round. Also, lung cancer screening with CT has a low positive predictive value, similar to the percentage of unnecessary surgeries performed in false positives. Another problem is that, at present, the burden of lung cancer overdiagnosis is not known. It is to be expected that if overdiagnosis occurs when thorax x-ray screening is used it will be greater when using CT. CT, even at low doses, exposes patients to high levels of radiation. Dealing with positive nodules entails an even higher radiation dose and the number of cancer cases induced by radiation in patients screened with CT is not known. Lastly, published studies on lung cancer CT screening are vastly heterogeneous. They include different age groups, different types of smokers and ex-smokers and different tomogram thickness, making the results hardly comparable. In this context we do not recommend lung cancer screening with CT for smokers or ex-smokers outside of the context of individual counseling.

The host support niche as a control point for tumor dormancy: implications for tumor development and beyond

An increasingly appreciated focus of carcinogenesis research is on mechanisms governing tumor growth after the fact of cancer cell creation. Of particular interest are dynamical interactions between tumor and host cell populations that can themselves strongly impact the fate of established cancer lesions. Regardless of tumor type, all cancers face the common problem of having to breach the barrier of angiogenic competency in order to advance from a microscopic lesion to symptomatic disease. If pre-angiogenic tumor cells are held in dormancy due to cell cycle arrest, this will postpone the need to traverse this higher-level barrier. On the other hand, the barrier itself may prove limiting to a tumor at its diffusion-limited size, creating a population-level dormancy characterized by balanced proliferation and cell death. In both cases of dormancy, the "angiogenic switch" has not yet occurred. We here describe and mathematically quantify an underappreciated third dormancy state defined by an angiogenic balance following the angiogenic switch. In this state we term "post-vascular dormancy," a tumor has attained angiogenic competency, but again demonstrates balanced proliferation and cell death because ambient pro- and anti-angiogenic influences are offsetting. Interestingly, autopsies have shown virtually all of us carry latent tumors in pre- or post-vascular states, many of which lie under the threshold of routine clinical detection. We show how, in the post-vascular case, tumor latency can arise from an elaborate mechanism of self-controlled growth, mediated through the tumor-vascular interaction. Underlying this observation is the finding that a tumor produces both angiogenesis stimulators and inhibitors, with the latter having greater influence, both locally and systemically, as the tumor grows-a mechanism we hypothesize is an aberrant co-option of normal organogenic regulation. That a tumor can limit its own growth raises the prospect that chronic therapies aimed at suppressing this tumor-host dynamic may compare favorably to current strategies which often yield favorable short-term responses but fail to deliver long-term tumor suppression.

Survival of patients with or without symptoms undergoing potentially curative resections for primary lung cancer

BACKGROUND

Numerous historical screening programs to detect lung cancer have been undertaken. With technologic advances, complimentary diagnostic tests have been developed; however, only the National Lung Cancer Trial has demonstrated increased survival. Following the success of this study, screening programs are being trialled in several countries. Screening should, in theory, reduce lung cancer deaths by identifying asymptomatic patients with earlier tumors. This study asked whether lung cancer patients who are asymptomatic at presentation have a better survival than those who present with symptoms.

METHODS

This was a retrospective analysis of a validated prospective thoracic surgery database from a tertiary center in the Northwest of England. Included were 1,546 consecutive patients (826 men, 720 women) who received operative intervention for non-small cell lung cancer. The main outcome measures included 5-year survival and univariate and multivariate Cox regression analysis.

RESULTS

Cancer stage, age, and operation type were confirmed as being of prognostic importance, validating previous studies. Survival between asymptomatic or symptomatic patients did not differ significantly (p = 0.489), regardless of stage. The hazard ratios (with 95% confidence intervals) for variables associated with poorer outcome identified by Cox's regression analysis were male sex, 1.34 (1.15 to 1.56); advancing age, 1.03 (1.02 to 1.04); advancing stage, 3.30 (2.69 to 4.04); and pneumonectomy, 1.24 (1.01 to 1.52). Symptoms were not a significant variable affecting survival on multivariate analysis.

CONCLUSIONS

This retrospective study from the Northwest of England showed that in our subset of lung cancer patients undergoing resection, asymptomatic patients with non-small cell lung cancer do not have improved survival, implying it is a systemic disease in many at diagnosis. Care should be taken when generalizing the results of the National Lung Screening Trial to all populations until further validation has been performed.

CT scan screening for lung cancer: risk factors for nodules and malignancy in a high-risk urban cohort

Background

Low-dose computed tomography (CT) for lung cancer screening can reduce lung cancer mortality. The National Lung Screening Trial reported a 20% reduction in lung cancer mortality in high-risk smokers. However, CT scanning is extremely sensitive and detects non-calcified nodules (NCNs) in 24–50% of subjects, suggesting an unacceptably high false-positive rate. We hypothesized that by reviewing demographic, clinical and nodule characteristics, we could identify risk factors associated with the presence of nodules on screening CT, and with the probability that a NCN was malignant.

Methods

We performed a longitudinal lung cancer biomarker discovery trial (NYU LCBC) that included low-dose CT-screening of high-risk individuals over 50 years of age, with more than 20 pack-year smoking histories, living in an urban setting, and with a potential for asbestos exposure. We used case-control studies to identify risk factors associated with the presence of nodules (n = 625) versus no nodules (n = 557), and lung cancer patients (n = 30) versus benign nodules (n = 128).

Results

The NYU LCBC followed 1182 study subjects prospectively over a 10-year period. We found 52% to have NCNs >4 mm on their baseline screen. Most of the nodules were stable, and 9.7% of solid and 26.2% of sub-solid nodules resolved. We diagnosed 30 lung cancers, 26 stage I. Three patients had synchronous primary lung cancers or multifocal disease. Thus, there were 33 lung cancers: 10 incident, and 23 prevalent. A sub-group of the prevalent group were stable for a prolonged period prior to diagnosis. These were all stage I at diagnosis and 12/13 were adenocarcinomas.

Conclusions

NCNs are common among CT-screened high-risk subjects and can often be managed conservatively. Risk factors for malignancy included increasing age, size and number of nodules, reduced FEV1 and FVC, and increased pack-years smoking. A sub-group of screen-detected cancers are slow-growing and may contribute to over-diagnosis and lead-time biases.

Use of lung cancer screening tests in the United States: results from the 2010 National Health Interview Survey

BACKGROUND

Before evidence of efficacy, lung cancer screening was being ordered by many physicians. The National Lung Screening Trial (NLST), which showed a 20% reduction in lung cancer mortality among those randomized to receive low-dose computed tomography (LDCT), will likely lead to increased screening use.

METHODS

We estimated the prevalence of chest X-ray and CT use in the United States using data from the 2010 National Health Interview Survey (NHIS). Subjects included 15,537 NHIS respondents aged ≥40 years without prior diagnosis of lung cancer. Estimates of the size of the U. S. population by age and smoking status were calculated. Multivariate logistic regression examined predictors of test use adjusting for potential confounders.

RESULTS

Twenty-three percent of adults reported chest X-ray in the previous year and 2.5% reported chest X-ray specifically to check for lung cancer; corresponding numbers for chest CT were 7.5% and 1.3%. Older age, black race, male gender, smoking, respiratory disease, personal history of cancer, and having health insurance were associated with test use. Approximately, 8.7 million adults in the United States would be eligible for LDCT screening according to NLST eligibility criteria.

CONCLUSIONS AND IMPACT

Monitoring of trends in the use of lung screening tests will be vital to assess the impact of NLST and possible changes in lung cancer screening recommendations and insurance coverage in the future. Education of patients by their physicians, and of the general public, may help ensure that screening is used appropriately, in those most likely to benefit.

Screening for lung cancer using low-dose spiral CT: 10 years later, state of the art

Ten years after the first papers on this subject, this editorial represents a brief review on lung cancer screening with low-dose spiral CT. The aim is to present the main theoretical and practical problems related to lung cancer screening, the historical background and results of observational studies and the main ongoing randomised controlled trials. In particular, the National Lung Screening Trial (NLST), which was interrupted early, is discussed. The opinion of the authors is that too many questions are still awaiting an answer.

Update on biomarkers for the detection of lung cancer

Patients at risk for lung cancer may have subclinical disease for years before presentation. The diagnosis of this disease is primarily based on symptoms, and detection often occurs after curative intervention is no longer possible. At present, no lung cancer early-detection biomarker is clinically available. This study reviews the most recent advances in early detection and molecular diagnostic biomarkers for the detection of lung cancer. This review includes an overview of the various biological specimens and matrices in which these biomarkers could be analyzed, as well as the diverse strategies and approaches for identifying new biomarkers that are currently being explored. Several novel and attractive biomarker candidates for the early detection of lung cancer exist. A remarkable shift is taking place from research based on single markers to analyzing signatures that are more complex in order to take advantage of new high-throughput technologies. However, it is still necessary to validate the most promising markers and the standardization of procedures that will lead to specific clinical applications.

Finding needles in a haystack: annual low-dose computed tomography screening reduces lung cancer mortality in a high-risk group

Lung cancer is a global health issue. Compared with other common malignancies, the prognosis is poor as many patients present with advanced disease. The National Lung Screening Trial (NLST) aimed to identify and treat early lung cancers using annual low-dose computed tomography (CT) screening in a high-risk group. When compared with chest x-ray screening, low-dose CT screening reduced lung cancer mortality by 20%; the NLST is the first lung cancer screening trial to demonstrate such a mortality benefit. However, we must wait for cost-effectiveness data from the NLST, as well as the results of ongoing European studies comparing low-dose CT with observation alone, before firm conclusions can be drawn regarding the overall benefits of introducing a CT screening program to clinical practice.

Comparing the benefits of screening for breast cancer and lung cancer using a novel natural history model

To estimate the impact of early detection of cancer, knowledge of how quickly primary tumors grow and at what size they shed lethal metastases is critical. We developed a natural history model of cancer to estimate the probability of disease-specific cure as a function of tumor size, the tumor volume doubling time (TVDT), and disease-specific mortality reduction achievable by screening. The model was applied to non-small-cell lung carcinoma (NSCLC) and invasive ductal carcinoma (IDC), separately. Model parameter estimates were based on Surveillance Epidemiology and End Results (SEER) cancer registry datasets and validated on screening trials. Compared to IDC, NSCLC is estimated to have a lower probability of disease-specific cure at the same detected tumor size, shed lethal metastases at smaller sizes (median: 19 mm for IDC versus 8 mm for NSCLC), have a TVDT that is almost half as long (median: 252 days for IDC versus 134 days for NSCLC). Consequently, NSCLC is associated with a lower mortality reduction from screening at the same screen detection threshold and screening interval. In summary, using a similar natural history model of cancer, we quantify the disease-specific curability attributable to screening for breast cancer, and separately lung cancer, in terms of the TVDT and onset of lethal metastases.

Lung cancer risk prediction: Prostate, Lung, Colorectal And Ovarian Cancer Screening Trial models and validation

INTRODUCTION

Identification of individuals at high risk for lung cancer should be of value to individuals, patients, clinicians, and researchers. Existing prediction models have only modest capabilities to classify persons at risk accurately.

METHODS

Prospective data from 70 962 control subjects in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) were used in models for the general population (model 1) and for a subcohort of ever-smokers (N = 38 254) (model 2). Both models included age, socioeconomic status (education), body mass index, family history of lung cancer, chronic obstructive pulmonary disease, recent chest x-ray, smoking status (never, former, or current), pack-years smoked, and smoking duration. Model 2 also included smoking quit-time (time in years since ever-smokers permanently quit smoking). External validation was performed with 44 223 PLCO intervention arm participants who completed a supplemental questionnaire and were subsequently followed. Known available risk factors were included in logistic regression models. Bootstrap optimism-corrected estimates of predictive performance were calculated (internal validation). Nonlinear relationships for age, pack-years smoked, smoking duration, and quit-time were modeled using restricted cubic splines. All reported P values are two-sided.

RESULTS

During follow-up (median 9.2 years) of the control arm subjects, 1040 lung cancers occurred. During follow-up of the external validation sample (median 3.0 years), 213 lung cancers occurred. For models 1 and 2, bootstrap optimism-corrected receiver operator characteristic area under the curves were 0.857 and 0.805, and calibration slopes (model-predicted probabilities vs observed probabilities) were 0.987 and 0.979, respectively. In the external validation sample, models 1 and 2 had area under the curves of 0.841 and 0.784, respectively. These models had high discrimination in women, men, whites, and nonwhites.

CONCLUSION

The PLCO lung cancer risk models demonstrate high discrimination and calibration.

Screening and early detection of lung cancer

Lung cancer with an estimated 342,000 deaths in 2008 (20% of total) is the most common cause of death from cancer, followed by colorectal cancer (12%), breast cancer (8%), and stomach cancer (7%) in Europe. In former smokers, the absolute lung cancer risk remains higher than in never-smokers; these data therefore call for effective secondary preventive measures for lung cancer in addition to smoking cessation programs. This review presents and discusses the most recent advances in the early detection and screening of lung cancer.An overview of randomized controlled computerized tomography-screening trials is given, and the role of bronchoscopy and new techniques is discussed. Finally, the approach of (noninvasive) biomarker testing in the blood, exhaled breath, sputum, and bronchoscopic specimen is reviewed.

Exploring the uncertainties of early detection results: model-based interpretation of mayo lung project

BACKGROUND

The Mayo Lung Project (MLP), a randomized controlled clinical trial of lung cancer screening conducted between 1971 and 1986 among male smokers aged 45 or above, demonstrated an increase in lung cancer survival since the time of diagnosis, but no reduction in lung cancer mortality. Whether this result necessarily indicates a lack of mortality benefit for screening remains controversial. A number of hypotheses have been proposed to explain the observed outcome, including over-diagnosis, screening sensitivity, and population heterogeneity (initial difference in lung cancer risks between the two trial arms). This study is intended to provide model-based testing for some of these important arguments.

METHOD

Using a micro-simulation model, the MISCAN-lung model, we explore the possible influence of screening sensitivity, systematic error, over-diagnosis and population heterogeneity.

RESULTS

Calibrating screening sensitivity, systematic error, or over-diagnosis does not noticeably improve the fit of the model, whereas calibrating population heterogeneity helps the model predict lung cancer incidence better.

CONCLUSIONS

Our conclusion is that the hypothesized imperfection in screening sensitivity, systematic error, and over-diagnosis do not in themselves explain the observed trial results. Model fit improvement achieved by accounting for population heterogeneity suggests a higher risk of cancer incidence in the intervention group as compared with the control group.

"Risk homeostasis"or "teachable moment"? the interaction between smoking behavior and lung cancer screening in the Mayo Lung Project

The chest X-ray lung cancer screening program of Mayo Lung Project (MLP) yielded mixed results of improved lung case survival but no improvement in lung cancer mortality. This paper analyzes the smoking patterns of study participants in order to examine possible behavioral ramifications of periodic lung cancer screening. Using a longitudinal difference-of-difference model, we compared the smoking behavior, in terms of current smoker status among all subjects and the intensity of smoking among those continuing smokers, between those who received periodic lung cancer screening and those who received usual-care. In both arms of this lung cancer screening trial, there was a sizable decline in cigarette smoking one year after participants received baseline prevalence screening. There was no significant difference in current smoker status between the intervention group receiving periodic X-ray screening and the control group receiving usual care. While we detect that the continuing smokers in the intervention group smoked more than their counterparts in the control group, the magnitude of the difference is not sufficient to explain a substantial difference in lung cancer incidence between the two groups. Our study shows that periodic lung screening in MLP did not decrease smoking behavior beyond the observed decline following the initial prevalence screening conducted at baseline for both the intervention and control groups. Our results also indicate, paradoxically, that participants assigned to the intervention group smoked more cigarettes per day on average than those in the control group. Lung cancer screening programs need additional cessation components to sustain the abstinence effect typically observed following initial lung screening.

Screening for lung cancer with low-dose computed tomography: a systematic review and meta-analysis of the baseline findings of randomized controlled trials

OBJECTIVES

Lung cancer is the leading cause of death among all cancers. An estimated 29% of the global population older than 15 years currently smokes tobacco. The presence of a high risk population, relatively asymptomatic nature of the disease in the early phase, and relatively good prognosis when discovered early makes screening for lung cancer an attractive proposition. We performed a systematic review and a meta-analysis of the baseline results of randomized controlled trials so far published, which included more than 14,000 patients. Analysis was used to determine whether data was for or against the screening of lung cancers using low-dose computed tomography (LDCT).

DESIGN

Random effect meta regression model of meta-analysis and systematic review.

METHODS

We performed a systematic review and a meta-analysis of the current literature to determine whether screening for lung cancer in a high-risk population with computed tomography improves outcomes. A search strategy using Medline was employed, studies selected based on preset criteria and application of exclusion criteria, and data collected and analyzed for statistical significance.

RESULTS

Screening for lung cancer using LDCT resulted in a significantly higher number of stage I lung cancers (odds ratio 3.9, 95% confidence interval [CI] 2.0-7.4), higher number of total non-small cell lung cancers (odds ratio 5.5, 95% CI 3.1-9.6), and higher total lung cancers (odds ratio 4.1, 95% CI 2.4-7.1). Screening using LDCT also resulted in increased detection of false-positive nodules (odds ratio 3.1, 95% CI 2.6-3.7) and more unnecessary thoracotomies for benign lesions (event rate 3.7 per 1000, 95% CI 3.5-3.8). For every 1000 individuals screened with LDCT for lung cancer, 9 stage I non-small cell lung cancer and 235 false-positive nodules were detected, and 4 thoracotomies for benign lesions were performed.

CONCLUSIONS

The baseline data from six randomized controlled trials offer no compelling data in favor or against the use of LDCT screening for lung cancer. We await the final results of these randomized controlled trials to improve our understanding of the effectiveness of LDCT in the screening for lung cancer and its effect on mortality.

Healthcare use after screening for lung cancer

BACKGROUND

To evaluate the benefits of lung cancer screening, all effects of screening need to be considered. The aim of this study was to determine whether screening had an effect on healthcare use, specifically whether use increased for those with a false-positive or indeterminate screening result.

METHODS

Recruited were 400 individuals participating in a lung cancer screening study at the University of Pittsburgh. Self-reported outpatient healthcare use information was collected for the 6 months before, 0 to 6 months after, and 6 to 12 months after screening. The screening outcomes were negative, indeterminate, and suspicious. Repeated-measures Poisson regression models were used to examine changes in use over time and how changes over time varied among the screening outcome groups.

RESULTS

Approximately 58% of participants had a negative screening result, 36% had an indeterminate result, and approximately 6% had a suspicious result. The percentage of individuals who had any incidence of each type of outpatient use increased after screening, with the greatest increase noted for those with a suspicious screening result. Adjusted mean use significantly increased for nearly all types of use and for all 3 screening results categories in the 6 months after screening, but mostly declined to prescreening levels in the next 6 months.

CONCLUSIONS

Outpatient healthcare use was found to increase after screening for all individuals who were screened for lung cancer, regardless of the screening finding. The cost of the lung-related visits alone was substantial. Therefore, if lung cancer screening prevalence is increased, attendant follow-up healthcare costs are also likely to increase.

Volunteer effect and compromised randomization in the Mayo Project of screening for lung cancer

It has been confirmed recently that the volunteer effect in lung cancer screening is characterized by higher lung cancer mortality risk in self-selected screening participants. The Mayo Lung Project, the most influential trial of screening for lung cancer ever completed, was conducted in nonvolunteer Mayo Clinic outpatients, with a peculiar study design that rendered the randomization vulnerable to the volunteer effect. Of all nonvolunteers randomized in the Mayo Lung Project, only those allocated in the screened group were asked consent to participate in the trial. The final Mayo Lung Project report stated that 655 randomized nonvolunteers refused screening and were excluded from the study, thus documenting violation of the rule that no selection should occur after randomization. The long-term follow-up of the Mayo Lung Project showed an enigmatic result which has never been explained: the lung cancer mortality was 13% higher in the screening intervention group than in the control group [4.4 (95% CI 3.9-4.9) vs. 3.9 (95% CI 3.5-4.4) per 1,000 person-years; P = 0.09]. Such overrepresented mortality is consistent with the volunteer effect and supports the concept that the Mayo Lung Project randomization was compromised by the post-randomization self-selection of participant nonvolunteers.

Screening for lung cancer: are we there yet?

PURPOSE OF REVIEW

In lung cancer screening with low-dose spiral computed tomography (LDCT), the proportion of stage I disease is 50-85%, and the survival rate for resected stage I disease can exceed 90%, but proof of real benefit in terms of lung cancer mortality reduction must come from the several randomized trials underway in Europe and in the USA. Our purpose is to update the readers on recent progress in medical knowledge in this field.

RECENT FINDINGS

Relevant novelties regarding technical and collateral aspects of lung cancer screening have been made available, covering the performance of detection systems and nodule evaluation protocols, means to increase cost-effectiveness, insight into the biology of lung cancer, promotion of minimally invasive and lung-sparing surgical options, effects of screening on smoking habits and early follow-up findings in one randomized trial of LDCT vs. clinical review.

CONCLUSION

Early follow-up data suggest that the effect of screening with LDCT on mortality might be smaller than expected, but definitive follow-up data are still awaited from all ongoing randomized trials. Lung cancer screening research is yielding a relevant body of medical knowledge that will be beneficial for other smoking-related diseases and contribute to a better understanding of lung cancer biology.