Twice as many lung cancers detected by CT as by X-ray at initial screening
Centers in the United States can achieve a 20% reduction in lung cancer mortality with low-dose computed tomography (LDCT) versus chest X-ray (CXR) screening that was previously reported by the National Lung Screening Trial (NLST). This reduction is achievable at experienced screening centers in the US.
This was the first of three planned annual screening examinations from the NLST. The NLST is a large-scale, longitudinal clinical trial that randomized over 53,400 study participants equally to receive either LDCT or standard CXR examinations with the goal of evaluating whether lung cancer screening saves lives. Results published in 2011 reported a 20% reduction in lung cancer deaths among study participants (all at high risk for the disease) screened with LDCT versus those screened with CXR.
"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," said biostatistician Timothy Church, PhD, of the University of Minnesota in Minneapolis. He also pointed out that a reduction in mortality is the ultimate indicator of a successful cancer screening strategy.
In the New England Journal of Medicine (2013; 365:395-409), the authors reported that the NLST initial-screening results were positive for LDCT versus CXR results, with more positive screening exams, more diagnostic procedures, more biopsies and other invasive procedures, and more lung cancers seen in the LDCT arm than in the CXR arm during the first screening round of NLST.
"Although we did see that CT resulted in referring more patients for additional testing, the question comes down to whether the 20% reduction in mortality is worth the additional morbidity introduced by screening high-risk patients," said Church. He noted that although the LDCT arm had more follow-up procedures than 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 (98.5%) in performing the LDCT examination as specified in the research protocol across the 33 imaging facilities that carried out the study."What we've learned from the analysis is that the first-screen results provide clinicians additional facts to discuss with patients who share similar characteristics as the NLST participants (current or former heavy smokers over the age of 55)," said Church. "The results also caution against making blanket lung cancer screening recommendations, because each person's trade-off between the risk of having an unnecessary procedure and the fear of dying of lung cancer is uniquely individual."