High-risk lung cancer patients with prior negative CT screening results have a high prevalence for the disease years later and should continue to be screened even three years after initial tests.
John Kavanagh, with the University Health Network in Toronto led the study in which 200 of the 327 subjects contacted participated. All patients had a negative screening result as part of the International Early Lung Cancer Action Program, and had not been screened for more than five years.
Participants averaged 74 years of age and were given a lung cancer risk score using a trusted risk model. They underwent low-dose CT between March 2013 and October 2016, according to the study published online July 10 in Radiology.
Kavanagh and colleagues found an estimated 5.6 percent incidence rate of developing lung cancer during the coming six years, with a period prevalence of 20.8 percent.
Low-dose CT discovered lung cancer in 14 of 200 subjects (7 percent), which authors noted was higher than the 1.1 to 2.7 percent range published in previous lung cancer screening studies. The 7 percent mark was also similar to the estimated risk score determined by the adopted risk model.
“Our study demonstrates that high-risk individuals with a history of several negative screening CT examinations remain at a high risk of developing lung cancer,” authors wrote.
The group argued that the number of individuals who died or developed lung cancer during the five-year interval following their negative scan findings (54 of 327) would likely have benefited from continuous screening, and therefore would recommend lessening the time between scans for this population.
“The results of our study demonstrate that individuals with negative screening results still have a significant risk of developing lung cancer in the longer term and that, although associated with substantial cost savings, screening at five-year intervals or longer after several scans is clinically and empirically inadequate,” Kavanagh and colleagues wrote.