Lung cancer is the leading cause of cancer death but there's still some uncertainty about whether the benefits of widespread CT scan screening outweigh the risks.
Hoping to shed light on the question, Peter B. Bach, M.D., of the Memorial Sloan-Kettering Cancer Center, New York, and colleagues conducted a systematic review to examine the evidence regarding the benefits and harms of low-dose computerized tomography (LDCT) screening for lung cancer.
“Most patients are diagnosed with advanced disease, resulting in a very low 5-year survival rate,” Bach and his colleagues wrote. “Renewed enthusiasm for lung screening arose with the advent of LDCT imaging, which is able to identify smaller nodules than can chest radiographs.” The researchers looked at a total of 31 studies of LDCT screening.
The most informative was the National Lung Screening Trial, which demonstrated that among 53,454 participants enrolled, screening resulted in significantly fewer (20%) lung cancer deaths but two smaller studies showed no such benefit.
“In terms of potential harms of LDCT screening, across all trials and cohorts, approximately 20 percent of individuals in each round of screening had positive results requiring some degree of follow-up, while approximately 1 percent had lung cancer," the authors wrote. “Low-dose computed tomography screening may benefit individuals at an increased risk for lung cancer, but uncertainty exists about the potential harms of screening and the generalizability of results.”
This report now forms the basis of the American College of Chest Physicians and the American Society of Clinical Oncology clinical practice guideline:
Recommendation 1: For smokers and former smokers ages 55 to 74 years who have smoked for 30 pack-years (number of packs of cigarettes smoked per day by the number of years the person has smoked) or more and either continue to smoke or have quit within the past 15 years, it is suggested that annual screening with LDCT should be offered over both annual screening with chest radiograph or no screening, but only in settings that can deliver the comprehensive care provided to National Lung Screening Trial participants. (Grade of evidence 2B, indicating a “weak recommendation based on moderate quality research data”)
Recommendation 2: For individuals who have accumulated fewer than 30 pack-years of smoking or are either younger than 55 years or older than 74 years, or individuals who quit smoking more than 15 years ago, and for individuals with severe comorbidities that would preclude potentially curative treatment, limit life expectancy, or both, it is suggested that CT screening should not be performed.