Computed Tomography Screening for Lung Cancer Detects Early

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Researchers affiliated with the International Early Lung Cancer Action Program Investigators have reported that Computed Tomography (CT) screening detects a higher percentage of early stage lung cancer than observed in a non-screened population. The details of this study appeared in the February 13, 2006, issue of the Archives of Internal Medicine .

There have been several recent studies evaluating the ability of baseline and repeat CT scanning to detect early lung cancer. However, there have been many doubts about the utility of this approach, including concern over excess false positives, cost-effectiveness and excessive exposure to radiation by repeat testing over a long period of time.

This study looked at baseline and repeat screening of over 28,000 individuals at high risk for developing lung cancer. This report concerns the characteristics of 689 people in this study diagnosed with lung cancer. There were 436 with non-small cell lung cancer (NSCLC) and 28 small cell lung cancer (SCLC). They observed that lesion size correlated with the presence of nodal metastasis.

In persons with NSCLC the proportion of cases with no metastases ranged from 91% of patients in whom the tumor was 15 mm or smaller, to 55% of those with tumors 36 mm or greater. They also observed that the size association was more positively correlated when the tumor was solid rather than par-solid. The relationship did not hold for non-solid tumors which were characterized as noninvasive adenocarcinomas or adenocarcinoma-mixed subtype with a small invasive component.

All of the SCLC were solid in nature and the proportion of cases with no metastases was 67% for tumors 25 mm or less versus 23% for larger tumors.

These authors concluded that lymph node status has a strong relationship to tumor diameter for NSCLC. They also reported that the percentages of N0 M0 cases in screen-diagnosed lung cancers were much higher than previously reported in the Surveillance, Epidemiology, and End Results registry (SEER).

Comments: These data suggest that screening CT detects lung cancers at an earlier stage than by symptomatic diagnosis as reflected by the SEER data. This should translate into improved survival following treatment. However, this will have to be documented in the ongoing randomized trial that is being conducted. In the absence of randomized trial data it would appear prudent to recommend screening CT for high risk individuals.

Reference: The International Early Lung Cancer Action Program Investigators. Computed tomographic screening for early lung cancer: The relationship of disease stage to tumor size. Arch Intern Med . 2006;166:321-325.