Early detection in lung cancer. Case finding and screening

Principles of cancer screening: lessons from history and study design issues

Early detection of cancer has held great promise and intuitive appeal in the medical community for well over a century. Its history developed in tandem with that of the periodic health examination, in which any deviations--subtle or glaring--from a clearly demarcated "normal" were to be rooted out, given the underlying hypothesis that diseases develop along progressive linear paths of increasing abnormalities. This model of disease development drove the logical deduction that early detection, by "breaking the chain" of cancer development, must be of benefit to affected individuals. In the latter half of the 20th century, researchers and guidelines organizations began to explicitly challenge the core assumptions underpinning many clinical practices. A move away from intuitive thinking began with the development of evidence-based medicine. One key method developed to explicitly quantify the overall risk-benefit profile of a given procedure was the analytic framework. The shift away from pure deductive reasoning and reliance on personal observation was driven, in part, by a rising awareness of critical biases in cancer screening that can mislead clinicians, including healthy volunteer bias, length-biased sampling, lead-time bias, and overdiagnosis. A new focus on the net balance of both benefits and harms when determining the overall worth of an intervention also arose: it was recognized that the potential downsides of early detection were frequently overlooked or discounted because screening is performed on basically healthy persons and initially involves relatively noninvasive methods. Although still inconsistently applied to early detection programs, policies, and belief systems in the United States, an evidence-based approach is essential to counteract the misleading--even potentially harmful--allure of intuition and individual observation.

Lung cancer screening--are we there yet?

BACKGROUND

Lung cancer is the most lethal cancer and most cases are the result of cigarette smoking. Although a high risk target population for screening can be defined, and although early stage lung cancer has a much better prognosis than advanced disease, there is still no clear evidence that lung cancer screening decreases mortality. Accordingly, current guidelines suggest that there is no evidence to support routine screening. Although randomized studies in the 1970('s) which used chest x-ray and sputum for screening were clearly negative in the last 20 years more sensitive screening tools such as chest computed tomography have revolutionized the field. However, randomized controlled trials of computed tomography have only recently been launched. AIMS OF THIS REVIEW: Our objectives are to provide the reader with the rationale for screening for lung cancer, to review the older screening studies and their limitations, and to summarize the current knowledge and ongoing trials of lung cancer screening.

LITERATURE SEARCH

A literature search using Medline was conducted from 1966 onwards searching for articles with relevant key words such as lung cancer screening chest X - ray low dose computerized tomography cancer screening guideline. When appropriate additional references were found from the bibliographies of identified papers of interest.

CONCLUSIONS

Recent uncontrolled multicenter studies of chest computed tomography scans show encouraging results. However, until data from, large properly designed and appropriately analyzed randomized controlled trials which may overcome research biases is available, the benefit of lung cancer screening, if any is still unknown.

Cancer screening: the clash of science and intuition

The concept of early detection of cancer holds great promise and intuitive appeal. However, powerful biases can mislead clinicians when evaluating the efficacy of screening tests by clinical observation alone. Selection bias, lead-time bias, length-biased sampling, and overdiagnosis are counterintuitive concepts with critical implications for early-detection efforts. This article explains these biases and other common confounders in cancer screening. The most direct and reliable way to avoid being led astray by intuitions is through the use of randomized controlled trials.

Diagnóstico precoce do câncer de pulmão: o grande desafio. Variáveis epidemiológicas e clínicas, estadiamento e tratamento

OBJETIVO: Avaliar casos confirmados de câncer de pulmão, revisando suas variáveis epidemiológicas, clínicas, estadiamento e tratamento. MÉTODOS: Foram estudados 263 casos provenientes do Hospital de Clínicas da Universidade Federal do Paraná e do Hospital Erasto Gaertner, instituições responsáveis por parcela significativa do atendimento a pacientes na cidade de Curitiba (PR). Realizou-se um estudo retrospectivo através de preenchimento de questionário e os dados obtidos foram analisados de forma descritiva, utilizando-se o software EPI-INFO. RESULTADOS: Houve predomínio de pacientes do sexo masculino (76%), sendo que a maioria dos pacientes era fumante ou ex-fumante por ocasião do diagnóstico (90%). Não havia referência a doença pulmonar prévia em 87% dos casos. Tosse (142 casos) e dor torácica (92 casos) foram os sintomas iniciais mais freqüentes. O câncer de pulmão tipo não pequenas células foi encontrado em 87% dos pacientes e o tipo histológico mais freqüente foi o carcinoma espinocelular, representando 49% dos casos. O tabagismo foi considerado o fator predisponente mais importante. CONCLUSÃO: As características evolutivas do câncer de pulmão, como a inespecificidade dos sintomas iniciais e o tempo e evolução do tumor, somadas à ausência de programas de rastreamento efetivos, constituem os principais fatores que contribuem para a não detecção da neoplasia pulmonar de forma precoce, o que torna difícil o tratamento e dificulta o aumento da sobrevida.

Chemoprevention Strategies for Patients with Lung Cancer in the Context of Screening

Despite major advances in the treatment and management of lung cancer, most patients with lung cancer eventually die of this disease. Because conventional therapies have failed to make a major impact on survival, newer approaches are necessary in the battle against lung cancer. Better understanding of molecular biology of several tumors has led to novel targeted therapeutic approaches with potential utility in cancer treatment in general and lung cancer in particular. In addition to smoking cessation, targeting individuals at high risk by use of early detection or aiming at reversal of premalignant lesions seem like attractive strategies. In light of the noted improvement in molecular diagnostic tools and targeted therapies, the question of chemoprevention in the context of early detection deserves a closer look. In this article, we review what has been achieved in the area of chemoprevention and discuss possible prospects that may help reduce lung cancer mortality in the context of early detection.

A new small cell lung cancer (SCLC)-specific marker discovered through antigenic subtraction of neuroblastoma cells

Small cell lung cancer (SCLC) is an aggressive form of lung cancer associated with cigarette smoking and presently accounts for approximately 20% of all lung cancer cases. SCLC cells derive from a neuroendocrine origin and therefore their antigenic profile coincides, to a great extent, with that of neuroendocrine cells. Multiple attempts to generate SCLC-specific MoAbs during the past decade have failed because all SCLC-specific MoAbs isolated also react against neuroendocrine tissues or normal immune cells. Cross-reactivity with normal antigens raises safety concerns due to the inevitable toxicity of such interactions and the dreaded effects. The concept of DIAAD trade mark ( Differential Immunization for Antigen and Antibody Discovery) provides for an immune response that can be effectively focused on cancer antigens. The object is to overcome obstacles resulting from an antigenic hierarchical pattern biased towards a response to dominant antigens in order to induce a robust immune response to cancer antigens. Cancer antigens are weak or nonimmunogenic molecules. Due to the fact that the immune system responds more strongly to immunodominant antigens than to weak immunogenic antigens, cancer cell proliferation is unencumbered. DIAAD employs protocols of induction of tolerance and immunity, conducted in sequential order to "biologically subtract" the immune response of dominant antigens expressed by normal cells. This biological subtraction is achieved in a laboratory animal by first eliminating the immune response to the normal cells or closely related cancer cells, followed by immunization of the same laboratory animal with diseased cells. This procedure directs the immune response exclusively towards antigens expressed by the diseased and not the normal cells. Our objective was to use DIAAD to generate monoclonal antibodies specific to SCLC antigens that are not shared by neuroendocrine cells by contrasting a pool of human SCLC cell lines with a pool of human neuroendocrine cancer cell lines. Four monoclonal antibodies reacted strongly and exclusively with SCLC cells and identified a membrane molecule comprising a single chain glycoprotein. Two of four antibodies were selected for a detailed analysis that revealed a narrow tissue specificity of antigen expressed by colon, lung, and pancreatic cancers (less than 20% staining was found on breast, ovarian and prostate cancer). These antibodies did not bind to various other cancers such as kidney, carcinoid, lymphoma, sarcoma, adrenal, liver, melanoma, seminoma, leiomyoma, basal cell cancer, or undifferentiated cancer. The epitope recognized by the selected MoAbs was destroyed with the removal of carbohydrates from SCLC cells. This result does not exclude the possibility of protein-carbohydrate cooperation in epitope recognition. However, it strongly suggests the pivotal role of carbohydrates in antibody binding to this molecule. Upon binding to the extracellular molecule on SCLC cells, the antibodies were shown to internalize. A low or insignificant level of internalization was recorded following incubation of the antibodies with neuroendocrine-derived tumors. The capacity of these antibodies to internalize upon binding the extracellular receptors renders them potential candidates for prodrug or immunotoxin-targeted therapeutics. In a qualitative experiment involving immunoaffinity purification, the SCLC antigen was shown to be differentially detected in sera of SCLC patients. Plans are being generated to explore the possible utility of this novel SCLC-specific antigen recognized by the above MoAbs as a new biomarker for early diagnosis of the disease, as well as for therapeutic intervention for SCLC.

Lung cancer and related risk factors: an update of the literature

At the present time, lung cancer is the leading cause of cancer-related death in males. Diagnostic difficulty makes detection complicated and this, in conjunction with the low survival rate, renders the disease a serious health problem. In-depth knowledge of associated risk factors is therefore called for, in order to prevent or at least reduce the appearance of lung cancer and to open new avenues of research. Although the disease has a multicausal aetiology, tobacco accounts for 85-90% of all cases. This paper reviews the current situation, dividing the risk factors, for study purposes, into two groups; intrinsic (non-modifiable) and extrinsic (modifiable).

DNA methylation as a cancer-specific biomarker: from molecules to populations

Cancer contributes to a large proportion of the mortality and morbidity in the United States and worldwide. Despite advances in diagnosis and treatment of various cancers, early detection and treatment of cancer remain a challenge. Diagnosis of cancer often occurs once the disease has progressed to a point where currently available intervention options provide limited success. Therefore, techniques that enable early detection followed by targeted interventions would influence stage at diagnosis and, in turn, mortality associated with cancer. Identification of molecular biomarkers, especially those that are associated with cancer initiation and progression, shows promise as an effective strategy in this regard. One potential early detection biomarker is DNA methylation of the promoter region of certain cancer-associated genes, which results in gene inactivation. Examination of serum for circulating tumor DNA with abnormal methylation patterns offers a possible method for early detection of several cancers and serves as a point for early intervention and prevention strategies. Additionally, it is imperative to consider how such a screening mechanism can be implemented in populations at risk, especially in resource-poor settings. Thus, the challenge is to validate DNA methylation as a cancer-specific biomarker, with the ultimate goal of designing a research plan that integrates the current knowledge base regarding cancer detection and diagnosis into specific prevention and intervention strategies that can be applied at a population level.

Computed tomography screening for lung cancer: back to basics

After some years in the doldrums, interest in screening for lung cancer is resurging. Conflicting evidence from previous lung cancer screening trials, based on plain chest radiography, has been the subject of much debate: the failure to demonstrate a reduction in mortality has led to the widely held conclusion that screening for lung cancer is ineffective. The validity of this assumption has been questioned sporadically and a large study currently under way in the U.S.A. should help settle the issue. Recently, there has been interest in the use of computed tomography to screen for lung cancer; radiation doses have been reduced to 'acceptable' levels and the superiority of computed tomography (CT) over chest radiography for the identification of pulmonary nodules is unquestioned. However, whether improved nodule detection will result in a reduction in mortality has not yet been demonstrated. The present review provides a historical background to the current interest in low-dose CT screening, explains the arguments that previous studies have provoked, and discusses the recent and evolving status of lung cancer screening with CT. Ellis, S. M. et al. (2001).

Lung cancer mortality in the Mayo Lung Project: impact of extended follow-up

BACKGROUND

The Mayo Lung Project (MLP) was a randomized, controlled clinical trial of lung cancer screening that was conducted in 9211 male smokers between 1971 and 1983. The intervention arm was offered chest x-ray and sputum cytology every 4 months for 6 years; the usual-care arm was advised at trial entry to receive the same tests annually. No lung cancer mortality benefit was evident at the end of the study. We have extended follow-up through 1996.

METHODS

A National Death Index-PLUS search was used to assign vital status and date and cause of death for 6523 participants with unknown information. The median survival for lung cancer patients diagnosed before July 1, 1983, was calculated by use of Kaplan-Meier estimates. Survival curves were compared with the log-rank test.

RESULTS

The median follow-up time was 20.5 years. Lung cancer mortality was 4.4 (95% confidence interval [CI] = 3.9-4.9) deaths per 1000 person-years in the intervention arm and 3.9 (95% CI = 3.5-4.4) in the usual-care arm (two-sided P: for difference =.09). For participants diagnosed with lung cancer before July 1, 1983, survival was better in the intervention arm (two-sided P: =.0039). The median survival for patients with resected early-stage disease was 16.0 years in the intervention arm versus 5.0 years in the usual-care arm.

CONCLUSIONS

Extended follow-up of MLP participants did not reveal a lung cancer mortality reduction for the intervention arm. Similar mortality but better survival for individuals in the intervention arm indicates that some lesions with limited clinical relevance may have been identified in the intervention arm.

Cancer screening

Especially in the emotionally charged field of cancer screening, which can have substantial public health implications for large numbers of healthy, asymptomatic people, it is important to achieve strong levels of evidence before promulgating new screening tools. This review of screening study methodology is intended to help the reader weigh such evidence and to evaluate reports which appear in the literature. It is an attempt to go beyond the often-stated intuition that early cancer detection finds cancers when they are easier to treat, at a time when survival is best. Examples tell us that sometimes this assumption has been true, sometimes not. A familiarity with the hidden biases in the supposition can be translated into everyday medical practice for screening tests in general. The practitioner can then match the strength of recommendation with the strength of the evidence behind the recommendation.

Correlation of tumor size and survival in patients with stage IA non-small cell lung cancer

OBJECTIVE

The purpose of this study was to determine the relationship between tumor size and survival in patients with stage IA non-small cell lung cancer (non-small cell lung cancer; ie, lesions < 3 cm).

METHOD

Five hundred ten patients with pathologic stage IA (T1N0M0) non-small cell lung cancer were identified from our tumor registry over an 18-year period (from 1981 to 1999). There were 285 men and 225 women, with a mean age of 63 years (range, 31 to 90 years). The Cox proportional model was used to examine the effect on survival. Tumor size was incorporated into the model as a linear effect and as categorical variables. The Kaplan-Meier product limit estimator was used to graphically display the relationship between the tumor size and survival.

RESULTS

The Cox proportional hazards model did not show a statistically significant relationship between tumor size and survival (p = 0.701) as a linear effect. Tumor size was then categorized into quartiles, and again there was no statistically significant difference in survival between groups (p = 0.597). Tumor size was also categorized into deciles, and there was no statistical relationship between tumor size and survival (p = 0.674).

CONCLUSIONS

This study confirms stratifying patients with stage IA non-small cell lung cancer in the same TNM classification, given no apparent difference in survival. Unfortunately, these data caution that improved small nodule detection with screening CT may not significantly improve lung cancer mortality. The appropriate prospective randomized trial appears warranted.

The normal CT appearances of the second carina and bronchial stump after left upper lobectomy

We retrospectively evaluated the computed tomography (CT) appearance of the bronchial stump and second carina (left upper lobe spur) after left upper lobectomy. There were 69 CT examinations in 38 patients; all were free of recurrent or metastatic disease. The spur was graded as a) sharp (wedge-shaped tip configuration with <90 degrees angulation), b) lobulated (bulbous tip with <90 degrees angulation), or c) widened (>90 degrees angulation regardless of tip configuration). The bronchial stump was evaluated for the presence or absence of soft tissue in proximity to the surgical staples. The spur had a sharp appearance in 33 of 38 patients (87%) and was lobulated in 5 of 38 (13%). No patient had soft tissue at the bronchial stump. Serial examinations showed no change in the appearance of either structure. The spur remains sharp after left upper lobectomy in most patients; lobulation occurs in 13%. No changes occur over time. Interval change, widening of the spur, or soft tissue at the bronchial stump may suggest abnormality. Knowledge of normal and potentially abnormal appearances is essential to proper CT interpretation, particularly in the setting of postoperative surveillance for recurrent or metastatic disease.

Detection of bronchial preneoplastic lesions and early lung cancer with fluorescence bronchoscopy: a study about its ambulatory feasibility under local anaesthesis

BACKGROUND

Autofluorescence bronchoscopy (AB) enhances the bronchoscopist's ability to diagnose bronchial preneoplastic lesions and early cancer. We undertook a study to assess its feasibility and performance under local anaesthesia on a real ambulatory mode.

METHODS

Thirty-four consecutive patients at very high risk for lung cancer were prospectively studied by AB under local anaesthesia, without any sedation. Lidocaine doses, time, oxygen saturation, peak expiratory flow (PEF) and the number of cough episodes were measured. Continuous assessment of the respiratory sensation was obtained with a visual analog scale. A total of 172 biopsies were performed in abnormal and normal areas.

RESULTS

The procedure was long-lasting (mean +/- SD: 26.6 +/- 6.0 min), required high total doses of Lidocaine (660 +/- 107 mg) without any significant side effect, and was associated with significant decreases in O2 saturation from 98.5 +/- 1.4 to 96.1 +/- 2.5% and in PEF from 380 +/- 96 to 310 +/- 78 l/min. However, the cough counts were moderate and the majority of patients reported no respiratory discomfort. 62 hyperplasia, metaplasia, dysplasia and carcinoma in situ (CIS) were detected and the relative sensitivity of AB +/- white-light bronchoscopy (WLB) versus WLB alone was 3.75 for intraepithelial lesions corresponding to moderate dysplasia or worse.

CONCLUSIONS

AB, a procedure that increases our ability to recognize preneoplastic lesions and early lung cancer, can be performed under local anaesthesia, without systemic sedation in patients at very high risk for lung cancer.

Screening for cancer in the patient with rheumatic disease

This article begins with a discussion of the types of cancer that are most often the target of cancer screening in general medical practice. Colorectal, prostate, cervical, and breast cancer screening guidelines are reviewed and some of the evidence (and controversy) behind these recommendations is discussed. A discussion of some of the special risks for cancer in patients with rheumatologic disease follows, and some modifications of standard screening guidelines are suggested for these high-risk patients.

Lung cancer

The primary prevention of lung cancer is to avoid and decrease the use of tobacco. Further research could include studying the effects of culture, ethnicity, and geographic location on smoking. Education needs to start early in the educational systems. At present there are programs for primary grades on drug and alcohol abuse and how to say "no." Education also needs to include the family when the parents are smokers, as their children are exposed to second-hand smoke and are led by example. Certain religious groups believe it is their duty to keep healthy and, therefore, do not smoke. These groups may be able to provide some answers as to how to prevent people from smoking. Prevention--it is our real hope.