Study sheds light on lung cancers that are undetected by radiograph

The findings will be presented Monday (Sept. 3, 2012) at the European Respiratory Society's Annual Congress in Vienna.

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 aren't 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 due to human error with the cancer being missed on the review of the radiograph, due to the cancer being undetectable by this form of screening technique, 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 aimed to analyse the type of people who developed this cancer and the characteristics of the disease.

The research used data from a national screening trial in the USA. It followed 77,445 participants who were screened at the start of the study and then annually for either 2 or 3 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 radiograph were spotted when it was re-reviewed. The remaining 65% of this group therefore had 'true interval cancer' which was not detected on the initial screening, or the second review.

The results revealed that these cancers were at a more advanced stage when diagnosed, were more often small cell lung cancers and less often adenocarcinoma. The analysis also showed that this type of cancer was more common among males and those with a history of smoking.

Lead author, Dr. Paul Kvale from the Henry Ford Hospital in the 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 programme. The results add to the evidence that a screening programme 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."