Results have major implications for lung cancer screening in Australia
A new study by Cancer Council NSW, published in the International Journal of Cancer, has – for the first time in Australia – evaluated the performance of a lung cancer risk prediction tool, the PLCOm2012, to predict current and ex-smokers at the highest risk for developing lung cancer.
In the future, the tool could help identify people suitable for lung cancer screening, and thus maximise the effectiveness of screening. The study found that the tool, which was developed in the USA and Canada, was able to reliably predict lung cancer diagnoses on the basis of a variety of risk factors in Australians.
Lung cancer screening has only been shown to be effective – and reduce mortality – in people at the highest risk of lung cancer, making targeting the right group essential. So far, identifying high risk groups has been an unsolved challenge in Australia, but Cancer Council NSW’s study successfully tested a promising method that has the potential to reduce the number of people who might be screened unnecessarily.
The study looked at how reliably the risk tool would predict lung cancer outcomes of almost 100,000 Australian current and ex-smokers who are part of the Sax Institute’s 45 and Up Study. The tool uses a mathematical formula to combine factors such as age, smoking intensity, duration and years quit, as well as additional factors such as body mass index and family history of lung cancer to predict someone’s risk of being diagnosed with lung cancer in the next 6 years.
“We compared the tool’s predictions with how many smokers in the Sax Institute’s 45 and Up study went on to develop lung cancer – and found that it had excellent predictive performance here in Australia,” said Dr Marianne Weber, Research Fellow at Cancer Council NSW.
The study examined the performance of the tool for a total of 1035 lung cancer diagnoses. In the 55-74 year age group (the age range likely to be targeted for screening), it correctly predicted nearly 70 per cent of all subsequent diagnoses.
“The tool was better at predicting those individuals who would go on to develop lung cancer than the guidelines that are currently being used to identify high risk individuals in the US and Europe,” Dr Weber added.
Lung cancer screening with low-dose computerised tomography (LDCT) is promising – it has been shown that lung cancer mortality can be reduced if detected and treated at an early stage. Early diagnosis of lung cancer is difficult, as the symptoms can often be vague and non-specific, and so the majority of cases are diagnosed at a late stage.
“Smoking is the primary factor that puts people at risk for lung cancer: 80 per cent of lung cancers are in people who were smokers. But screening everyone who has ever smoked a cigarette is not feasible and would potentially cause unnecessary testing, costs, and psychological distress,” Dr Weber explained.
“Harms of screening include adverse psychological effects, invasive follow-up testing because of false-positive screens and over-diagnosis, with the potential for people to undergo unnecessary invasive procedures.”
Applying a risk prediction tool to identify people who are at the highest risk has the potential to reduce the number of people needing to be screened, as well as the number of false positives, and has potential to make screening more efficient and cost-effective.
“Our study has major implications for the future of lung cancer screening in Australia – it’s the biggest cohort ever analysed with this tool, and the tool’s performance is extremely promising. Using our results, we estimate that around 29% of people who have ever smoked may be eligible for screening according to the tool, by the time they are 55 years old,” Dr Weber said.
“However, there is also a pressing need for more data and evidence, to confirm the effectiveness of screening those identified as high risk via the use of the tool. There is a joint Australian and Canadian trial underway that will further validate the tool and optimise the trade-off between screening benefits and harms.”
Doctor Martin McNamara, Head of Research Assets at the Sax Institute, said these findings demonstrated the value of large-scale, longitudinal studies like the 45 and Up Study.
“This research has the potential to be a real game-changer in the fight against lung cancer and the 45 and Up Study has been crucial to this by allowing Dr Weber, the team at Cancer Council NSW, and their collaborators to compare the predictive tool with the real world outcomes,” said Dr McNamara. “The scale, scope and longevity of the 45 and Up Study enables pioneering organisations like Cancer Council NSW to answer big public health questions like this.”
Cancer Council NSW urges policy makers to put the focus on prevention through the investment in, and implementation of, a comprehensive approach to tobacco control, as screening is not an alternative to smoking cessation.
“It is important to note that in the absence of further evidence in Australia there are currently no plans for a lung cancer screening program. The best way to reduce your risk of lung cancer is – and always will be – to quit smoking and stay quit,” Dr Weber concluded.
- PLCOm2012 – the risk prediction tool – was developed in a population of screening trial participants in the United States. This study applied the tool to local data, to evaluate its performance in the Australian context.
- “Identifying high risk individuals for targeted lung cancer screening: independent validation of the PLCOm2012 risk prediction tool” is a study by Cancer Council NSW researchers published in the International Journal of Cancer.
- PLCOm2012 – the risk prediction tool – is a logistic regression model, developed in a population of screening trial participants in the United States.
- Using sociodemographic and health factors such as smoking intensity, duration, and years quit, it predicts 6-year lung cancer risk in smokers.
- The Cancer Council NSW study aimed to validate the performance of the PLCOm2012 model in predicting lung cancer outcomes in a cohort of Australian smokers.
- The risk was calculated by applying PLCOm2012 to baseline data from 95,882 smokers over 45 years in the Sax Institute’s 45 and Up Study (2006-2009).
- The Sax Institute’s 45 and Up Study is the largest ongoing study of healthy ageing in the Southern Hemisphere, involving a quarter of a million people – one in every 10 men and women aged 45 and over in NSW.
Source: Cancer Council NSW