Interval LDCT Screening Increases Lung Cancer Detection

Low-dose CT screening with increasing intervals can help detect lung cancer among high-risk individuals, according to a study published in The Lancet Oncology. 

Researchers from the Netherlands sought to assess screening test performance, and the epidemiological, radiological, and clinical characteristics of interval cancers in NELSON trial participants assigned to the screening group. The NELSON trial was a randomized trial designed to investigate if screening with low-dose CT would help decrease 10-year lung cancer mortality among high-risk subjects.  

High-risk subjects were those aged 50 to 75 and who were current smokers who smoked 15 or more cigarettes per day for more than 25 years, or 10 or more cigarettes for more than 30 years, as well as people who had quit smoking less than 10 years ago. Participants in the NELSON trial were randomly assigned to low-dose CT screening at increasing intervals (7,915 participants), or no screening (7,907 participants). For this study, researchers assessed 7,155 participants, with median follow-up of 8.16 years.

Initial screenings evaluated nodule presence and volume, which were classified as negative, indeterminate, or positive. Subjects who were classified as indeterminate underwent follow-up screening for further classification of negative or positive, based on volume doubling time. ”We obtained information about all lung cancer diagnoses made during the first three rounds of screening, plus an additional two years of follow-up from the national cancer registry,” the authors wrote. “We determined epidemiological, radiological, participant, and tumor characteristics by reassessing medical files, screening CTs, and clinical CTs.”

The results showed that 187 (3%) of the 7,155 screened participants were diagnosed with 196 screen-detected lung cancers. Thirty-four more patients were diagnosed later with 35 interval cancers: 19 within the first year after screening and 15 in the second year.

Three screening rounds combined at two-year follow-up showed:

• Sensitivity - 84.6%

• Specificity - 98.6%

• Positive predictive value – 40.4%

• Negative predictive value – 99.8%

Interval cancers were not visible in 12 cases (35%) of the 34 patients, the researchers noted during retrospective assessment. These were missed due to:

• Radiological detection and interpretation errors, 17 cases (50%)

• Misclassification by the protocol, two cases (6%)

• Participant non-compliance, two cases (6%)

• Non-adherence to protocol, one case (3%)

Comparison of interval-detected cancers with screen-detected cancers:

“Lung cancer screening in the NELSON trial yielded high specificity and sensitivity, with only a small number of interval cancers,” the researchers concluded. “The results of this study could be used to improve screening algorithms, and reduce the number of missed cancers.”