Almost two-thirds of asbestos-exposed patients with lung cancer would not meet the proposed criteria for a national screening program, an Australian study suggests.
Last year, the Medical Services Advisory Committee recommended the Federal Government implement a national lung cancer screening program using low dose computed tomography (LDCT) that would cover long-term smokers and former smokers aged between 55 and 70.
However, researchers, led by Curtin University in WA, say their study shows that LDCT screening is effective at identifying early-stage cancer in an asbestos-exposed population and may warrant expanding the screening criteria to include occupational exposures.
They analysed data from 1743 people (median age 70) participating in an asbestos health surveillance program in Western Australia who underwent at least one LDCT scan and lung function assessment as part of an annual review over a five-year period from 2012 until 2017.
Of those screened, 85% were male and two-thirds were ever smokers.
Overall, 26 lung cancers were identified over the study period, equating to 1.5% of the total population or 3.5 cases per 1000 person-years of observation.
Nineteen cases were detected on LDCT within the five-year CT period, and a further three cases had nodules detected at year five with lung cancer diagnosed during the following year.
The remaining four cases were diagnosed in patients who had withdrawn from the review program, of which three were interval cancers and one had a 4mm nodule on the last LDCT.
Most lung cancer (86%) was early stage and four cases (15%) were among never smokers.
“A significant majority of this population (75%) would have been ineligible for any current or proposed LCSP, including 65% of the lung cancers cases. This highlights the importance of the risk conferred by asbestos exposure, independent of tobacco smoke exposure,” the authors wrote in Respirology [link here].
Among other findings, asbestosis was present on CT for 602 participants (35%), pleural plaques confirming significant asbestos exposure was present in 1066 (61%), emphysema was present in 254 (15%) and spirometry-defined COPD was present in 206 (12%).
Lead author respiratory physician Professor Fraser Brims, from Sir Charles Gairdner Hospital and Curtin University, said any proposed risk model would have to be easily implemented to be effective and have clear eligibility criteria, such as the amount of time exposed to asbestos.
However, he said more work was required at a population level to make a strong scientific and economic case for expanding the “very conservative set of risk criteria” proposed by MSAC.
“The key message from the study is that we found a high risk population who are not currently covered well by any risk criteria [for lung cancer screening],” he told the limbic.
“So there is an implementation gap and knowledge gap as to how we identify a population at risk of lung cancer beyond just tobacco and age, which are the biggest two drivers.
“The next piece of work is to actually work out how we can do that effectively and efficiently.”