Compared to X-rays, Twice as Many Lung Tumors Detected by CT at Initial Screening

Investigators concluded that the 20% decrease in lung cancer mortality using low-dose computed tomography (LDCT) imaging versus chest X-ray (CXR) screening reported in a new study is attainable.

Physicians have more information to share with their patients about the benefits and risks of LDCT lung cancer screening following the May 27, 2013, publication in the New England Journal of Medicine of the results of the first (of three planned) yearly screening examinations from the US National Lung Screening Trial (NLST).

“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,” stated Timothy Church, PhD, a biostatistician and professor in the School of Public Health at the University of Minnesota (Twin Cities, MN, USAu), who has been involved with the NLST’s design, implementation, and analysis.

Dr. Church also stressed that a reduction in mortality is the fundamental indicator of an effective cancer screening approach. 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 findings were published May 22, 2013, in the New England Journal of Medicine (NEJM). Earlier results published in 2011 in NEJM reported a 20% reduction in lung cancer deaths among study participants (all at high risk for the disease) screened with LDCT vs. those screened with CXR.

The authors reported that the NLST initial-screening findings are similar to other large trials with regard to positive LDCT versus CXR results, with more positive screening exams [7191 vs. 2387, respectively], more diagnostic procedures [6369 vs. 2176, respectively], more biopsies and other invasive procedures [297 vs. 121, respectively], and more lung tumors seen in the LDCT arm than in the CXR arm during the first screening round of NLST [292 vs. 190, respectively]. Although these findings were mostly anticipated, a key reason to publish the data was to validate the precise 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% reduction in mortality is worth the additional morbidity introduced by screening high-risk patients,” remarked Dr. Church. He noted that although there were more follow-up procedures in the LDCT versus the CXR arm, it was encouraging to validate that the number of individuals who actually had a more invasive follow-up procedure was very small.

Other promising findings reported include the high rate of compliance in performing the LDCT scan as indicated in the research protocol across the 33 imaging facilities that performed the study. “The sites complied with the low-dose CT imaging protocol specifications in 98.5% of all studies performed, which is outstanding considering the many thousands of scans performed,” stated Denise R. Aberle, MD, the US lead investigator for NLST ACRIN (American College of Radiology Imaging Network) and site co-lead investigator for the University of California, Los Angeles (UCLA; USA) NLST team.

Dr. Aberle, a member of the UCLA Jonsson Comprehensive Cancer Center, professor of Radiology and Bioengineering and vice chair for research in radiology at UCLA, also stressed that the first-screen result greatly 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 apt to have results similar to those reported in the study.

“What we’ve learned from the analysis of the first-screen results provides 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],” noted Dr. 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.”

“[This] publication represents the type of immensely important data NLST will continue to provide about lung cancer screening in the United States,” said Mitchell J. Schnall, MD, PhD, ACRIN network chair, group cochair of the ECOG-ACRIN Cancer Research Group and chair of the radiology department of the University of Pennsylvania (Philadelphia, PA, USA).

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University of Minnesota
University of California, Los Angeles