Wednesday, November 17, 2010

CTing the risk of dying from lung cancer.

Is CT scan is to lung cancer what Pap smear is to cervical cancer?  Can routine CT-scan screening detect asymptomatic lung cancer and improve the odds of someone being a "lung cancer survivor."  The results of the NCI-sponsored National Lung Screen Trial (NLST) released recently, would like you to believe, yes, it is.

NLS Trial which started in August 2002, compared low-dose CT scan and conventional chest x-ray as a screening tool for lung cancer.  With 53,500 current or former smokers (participants), aged 55-74 years with a history of 30 pack years (1 pack year = 1 pack of cigarette per day per year) but with no sign, symptom or history of lung cancer, the trial concluded that participants who were screened with CT scan (scans at 1st and 2nd year of study) had better chance of cancer detection, resulting in 20 % less chance of death due of lung cancer compared to x-ray cohort five years later (5th year.)  

Lung cancer accounts for about 25% of all cancer deaths in US and exerts a deep emotional and financial burden.  Although smoking cessation programs have made a significant dent, there are still over 90 million current and former smokers in US.  The 5 year survival from lung cancer is 70% with surgical resection of stage 1A (i.e. early) disease; however, these account for only one-quarter of all diagnosed lung cancers.  In those with advanced or metastatic disease, the survival statistics is very grim, just 5%.  Thus, development or validation of a reliable screening method is of high priority.  So far, the available screening methods (chest x-ray, bronchoscopy or sputum cytology) have not shown to lower the risk of death, in part, due to the fact that early symptoms are often missed or misdiagnosed as infections, pneumonia, cardiovascular disease, etc. 

This is the first time that a screening method was shown to decrease the risk of  death in lung cancer.  This is a very significant finding but not without controversies, including
  • over-exposure to radiation (multiple CT scans)
  • risk of additional invasive diagnostics
  • false positives resulting in significant anxiety and expense – one-fourth of all CT scans in the study showed abnormalities, most turned out to be benign, but it raises significant emotional and cost issues, with the risk of patients been subjected to unnecessary (sometimes, driven by physicians' bottom lines) lung biopsies or thoracic surgeries which themselves are not without complications.
  • and cost, patient access and medical coverage issues.

CT scan technology will definitely continue to evolve, but simple blood or prick tests are also sorely needed – unless there is dumbing down of technology, screening cannot be as widespread as one hopes to.

Further Reading:
NLST, the National Lung Screening Trial Update @
The National Lung Screening Trial: Overview and Study Design.  Radiology November 2, 2010 | PubMed | DOI |
Lung Cancer Wikipedia,,  American Cancer Society - non-small cell lung cancer

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