New Data Provide Clues into Why Some Lung Tumors Are Undetected by X-Ray

The study’s findings were presented on September 3, 2012, at the European Respiratory Society’s annual Congress in Vienna (Austria). There has been no significant reduction in lung cancer-mortality rates in recent years. Chest radiographs can be used to screen for lung cancer. However, these are not always effective and it appears that some cancers are later diagnosed even though individuals have received a negative chest radiograph within the previous 12 months.

The reason for this could be caused by human error with the tumor being missed on the review of the radiograph, due to the cancer being undetectable by this form of screening modality, or because the cancer developed so rapidly that it both initiates and becomes evident in the time interval between screening tests.

Little is known about this form of lung cancer that is not detected by screening chest radiograph, which is referred to as an interval cancer. To improve the understanding of this type of the disease, researchers geared to analyze the type of people who developed this cancer and the characteristics of the disease.

The researchers utilized data from a US screening trial in the United States. It followed 77,445 participants who were screened at the start of the study and then annually for either two or three years depending on their smoking status. A total of 450 people were diagnosed with lung cancer during the years of chest radiograph screening, of which 152 were initially not spotted by the radiograph. Out of this group, 35% of lung cancers not initially identified on the X-ray were spotted when it was re-reviewed. The remaining 65% of this group therefore had “true interval cancer” that was not detected on the initial screening, or the second review.

The study’s findings revealed that these tumors were at a more advanced stage when diagnosed, were more often small-cell lung cancers and less frequently adenocarcinoma. The analysis also demonstrated that this type of cancer was more typical among males and those with a history of smoking.

Lead author, Dr. Paul Kvale, from the Henry Ford Hospital (Detroit, MI, USA), said, “These findings have helped us to understand the characteristics of this type of lung cancer, pointing out features which make them different from lung cancers that can be detected by a chest X-ray screening program. The results add to the evidence that a screening program using X-rays is not suitable for lung cancer, as this this more aggressive form of the disease will be missed. By increasing our understanding of true interval cancers, we can help to improve screening techniques in the future.”

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