Screening: CT Detects More Lung Cancers as X-ray

Photo: CT image of lung

The number of early-stage cancers detected in the trial's CT arm were significantly greater than the number detected in the chest X-ray arm;
© Malov

National Lung Screening Trial (NLST) investigators conclude that the 20 percent reduction in lung cancer mortality with low-dose computed tomography (LDCT) versus chest X-ray (CXR) screening is achievable at experienced screening centers in the United States.

"For a cancer screening to work, it's important to verify that it can in fact discover cancers early. The analysis of NLST participants' initial annual screening examination provides evidence that the number of early-stage cancers detected in the trial's CT arm were significantly greater than the number detected in the chest X-ray arm," says Doctor Timothy Church of the University of Minnesota.

Church also points out that a reduction in mortality is the ultimate indicator of a successful cancer screening strategy. The NLST is a large-scale, longitudinal clinical trial that randomized over 53,400 study participants equally into either the LDCT or standard CXR arm to evaluate whether lung cancer screening saves lives. The results of the study reported a 20 percent reduction in lung cancer deaths among study participants (all at high risk for the disease) screened with LDCT versus those screened with CXR.

The authors say that the NLST initial-screening results are reflective of other large trials with regard to positive LDCT versus CXR results, with more positive screening exams (7191 versus 2387, respectively), more diagnostic procedures (6369 versus 2176, respectively), more biopsies and other invasive procedures (297 versus 121, respectively), and more lung cancers seen in the LDCT arm than in the CXR arm during the first screening round of NLST (292 versus 190, respectively). Although these results were generally anticipated, a key reason to publish the data was to document the exact differences between the two arms. "Although we did see that CT resulted in referring more patients for additional testing, the question comes down to whether the 20 percent reduction in mortality is worth the additional morbidity introduced by screening high-risk patients," says Church. He notes that although there were more follow-up procedures in the LDCT versus the CXR arm, it was encouraging to confirm that the number of individuals who actually had a more invasive follow-up procedure was quite small.

Another encouraging result reported is the high rate of compliance in performing the LDCT examination as specified in the research protocol across the 33 imaging facilities that carried out the study. "The sites complied with the low-dose CT imaging protocol specifications in 98.5 percent of all studies performed, which is outstanding considering the many thousands of scans performed," states Doctor Denise R. Aberle. Aberle also emphasizes that the first-screen result strongly suggests that CT lung cancer screening programs with radiologists who possess similar expertise and interpret similar numbers of CT cases that are obtained on scanners of the same caliber or better as those required for the NLST are likely to have results similar to those reported in the study.; Source: American College of Radiology