Is it useful to combine sputum cytology and low-dose spiral computed tomography for early detection of lung cancer in formerly asbestos-exposed power industry workers?

Our plain-English summary of Is it useful to combine sputum cytology and low-dose spiral computed tomography for early detection of lung cancer in formerly asbestos-exposed power industry workers?, by M.K. Felten, L. Knoll, C. Schikowsky, et al (Journal of Occupational Medicine and Toxicology, 2014).

The study

• Authors: M.K. Felten, L. Knoll, C. Schikowsky, M. Das, C. Feldhaus, K.G. Hering, A. Böcking, T. Kraus
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2014;9:14
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Low-dose spiral computed tomography (LDSCT) in comparison to conventional chest X-ray proved to be a highly sensitive method of diagnosing early stage lung cancer. However, centrally located early stage lung tumours remain a diagnostic challenge. We determined the practicability and efficacy of early detection of lung cancer when combining LDSCT and sputum cytology.

Methods: Of a cohort of 4446 formerly asbestos exposed power industry workers, we examined a subgroup of 187 (4.2%) high risk participants for lung cancer at least once with both LDSCT and sputum cytology. After the examination period the participants were followed-up for more than three years.

Results: The examinations resulted in the diagnosis of lung cancer in 12 participants (6.4%). Six were in clinical stage I. We found 10 non-small cell lung carcinomas and one small cell lung carcinoma. Sputum specimens showed suspicious pathological findings in seven cases and in 11 cases the results of LDSCT indicated malignancies. The overall sensitivity and specificity of sputum cytology was 58.0% and 98% with positive (PPV) and negative (NPV) predictive values of 70% and 97%. For LDSCT we calculated the sensitivity and specificity of 92% and 97%. The PPV and NPV were 65% and 99% respectively.

Conclusions: Our results confirmed that in surveillance programmes a combination of sputum cytology and LDSCT is well feasible and accepted by the participants. Sputum examination alone is not effective enough for the detection of lung cancer, especially at early stage. Even in well- defined risk groups highly exposed to asbestos, we cannot recommend the use of combined LDSCT and sputum cytology examinations as long as no survival benefit has been proved for the combination of both methods. For ensuring low rates of false-positive and false-negative results, programme planners must closely cooperate with experienced medical practitioners and pathologists in a well-functioning interdisciplinary network.

In plain English

This German study tested whether combining low-dose spiral CT scans of the chest with sputum cytology (checking coughed-up mucus for abnormal cells) helps detect lung cancer early in former power industry workers exposed to asbestos. From a cohort of 5632 workers, the authors analysed 187 judged at high risk from their age, smoking and years of asbestos exposure. These participants were examined with both tests until July 2006 and followed to the end of 2009. Twelve participants (6.4%) were diagnosed with lung cancer during the active study period. Sputum cytology detected 58% of the cancers and correctly cleared 98% of those without cancer; the CT figures were 92% and 97%. Used together, the two tests detected 100% of the cancers, but only 60% of positive results proved to be cancer. Six further cancers arose between or after examinations in people with no earlier abnormal findings. The authors concluded that the combination was feasible and accepted by participants, and that sputum alone was not effective for early-stage cancer. They also concluded that the combination could not be generally recommended without evidence of reduced mortality. They called the small group and limited follow-up serious limitations.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Health surveillance (screening) study of a high-risk subgroup examined with both low-dose spiral CT and sputum cytology, followed by a follow-up period for new lung cancer cases
• Who was studied: 187 high-risk participants, aged no more than 75 on 1 September 2002, from a cohort of 5632 formerly asbestos-exposed employees of a major electrical power provider in Germany. They were selected by a score combining exposure duration, age and smoking, and 76 were excluded for missing or unusable test results. Examinations ran until July 2006 and follow-up until the end of 2009.
• Exposure: Asbestos exposure during maintenance and repair work in power generation installations, including removal of asbestos lagging around turbines and spraying of asbestos pulp, without effective protection. Mean exposure duration was 29.5 years (range 15 to 49). No fiber type is named.
• Main results:
  • 12 of the 187 participants (6.4%) were newly diagnosed with lung cancer during the active study period; 11 were confirmed by lung tissue biopsy
  • Of the 11 biopsy-confirmed cases, six were in clinical stage I; there were ten non-small cell and one small cell lung carcinoma
  • Sputum cytology showed suspicious or pathological findings in 7 of the lung cancer cases
  • Sputum cytology: sensitivity 58%, specificity 98%, positive predictive value 70%, negative predictive value 97%
  • Low-dose spiral CT: sensitivity 92%, specificity 97%, positive predictive value 65%, negative predictive value 99%
  • False-positive rates were 1.7% for sputum cytology (3 of 175) and 3.4% for CT (6 of 175)
  • Both methods combined: sensitivity 100%, specificity 95%, positive predictive value 60%, negative predictive value 100%
  • Sputum cytology detected one centrally located tumour (stage IIIb) that was not visible on CT
  • Sputum cytology diagnosed centrally located tumours more often (83%) than peripheral tumours (33%)
  • Six further lung cancers occurred: two between routine examinations and four after the examination period up to the end of 2009. None of these patients had had pathological or equivocal findings on earlier tests.
• The authors' conclusion: The authors concluded that combining sputum cytology and CT is feasible and accepted by participants, and that sputum examination alone is not effective for early-stage lung cancer. They judged the combination probably more effective than CT alone in high-risk individuals, but said it cannot be generally recommended without evidence of reduced mortality and improved overall survival.
• Limitations the authors state:
  • The study group was small and the follow-up period was limited
  • Lung cancer cases not reported to the accident insurance register, or misdiagnosed on death certificates, may have been missed
  • Exposure data came from self-administered questionnaires and may be affected by recall bias
  • The study could not assess the overall effectiveness of lung cancer screening in asbestos-exposed people
  • Sputum was collected at home rather than induced; induced sputum would have given better samples and more valid results

Topics

Medical terms in this study, explained in our Lexicon: Sputum, Cytology, Lung Cancer, Chest X-Ray, Carcinoma.

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• Early detection of interstitial lung disease in asbestos exposed non-smoking workers by mid-expiratory flow rate and high resolution computed tomography — Z. Dujić, J. Tocilj, et al. (1991)
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• Computed tomography in the early detection of asbestosis — R. Bégin, G. Ostiguy, et al. (1993)
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