Estimates of the eligible population for Australia’s targeted National Lung Cancer Screening Program, 2025–2030

Introduction

Australia is preparing to launch a targeted National Lung Cancer Screening Program starting in July 2025.¹ The program will be open to individuals aged 50–70 years with a 30 pack-year smoking history (equivalent to a pack of 20 cigarettes per day for 30 years), who either currently smoke or have quit within the past 10 years. These criteria were recommended by Australia’s Medical Services Advisory Committee based on evidence from effectiveness trials and economic modelling.¹ Eligibility will be assessed by primary care providers (GPs, Aboriginal and Torres Strait Islander Health Workers, etc) who will refer participants to receive a low-dose computed tomography scan of the chest every 2 years.² Estimates of the number of people who qualify for lung cancer screening are important for understanding the impact of screening on resource use across the screening and assessment pathway and for program evaluation over time. Since there is no comprehensive collection of data on smoking behaviours at a population level, we forecasted the number of screening-eligible individuals over the first 5 years of the program using a statistical modelling approach.

Methods

The number of individuals who meet the lung cancer screening age and smoking history eligibility criteria over the period 2025–2030 was estimated using data from the 2019 National Drug Strategy Household Survey³ and 2022 Australian Bureau of Statistics population projections.⁴ Multiple imputation integrated with predictive modelling of future or unmeasured smoking characteristics was used to address missing data and, simultaneously, to project individuals’ smoking histories to 2030.

For each respondent, we required calculations of: 1) The age that they started smoking daily and the age that they stopped (if they stopped); 2) The duration that they had smoked or will smoke (if they started or start); 3) The lifetime average number of cigarettes per day, both factory made and roll-your-own (past and future). Pack-years were calculated as the number of years smoked multiplied by the number of cigarette packs smoked per day, assuming 20 cigarettes per pack.

Values of key smoking-related variables were imputed/predicted using demographic factors and other covariates (see supplementary material, available from m9.figshare.27936513.v1). Age at smoking initiation and smoking duration were modelled with accelerated failure time models and all remaining variables were modelled with random forests. For each state and year, we predicted the proportion of the population eligible for screening using logistic regression. Weights were adjusted to sum to the effective sample size proposed by Kish⁵, and 95% prediction intervals were estimated by sampling regression parameters from the asymptotic distribution in each imputed dataset, then pooling all predictions of the eligible population.

Detailed methods are reported in the supplementary material, available from m9.figshare.27936513.v1.

Results

Overall, between 12.8–14.1% of the Australian population aged 50–70 years were estimated to meet the National Lung Cancer Screening Program age and smoking criteria in the first 5 years of the program (30–33% of those with a history of smoking). In the first year, 930,500 (95% prediction interval 852,200–1,019,000) individuals were estimated to be eligible, with the number meeting the criteria in each state and territory declining slightly over the years 2025–2030 (see Table 1). Overall, 26-30% of those eligible will have quit smoking, and 70-74% will currently smoke.

Discussion

Using individual-level, nationally representative data about smoking status, duration, intensity and years since quitting smoking (if quit), we projected smoking characteristics for the Australian population up to the year 2030 by age. By applying the age and smoking eligibility criteria for the National Lung Cancer Screening Program, these estimates represent the total number of individuals who may qualify for screening in any particular year.

We find that around a third of the ever-smoking population would be eligible for lung cancer screening, which is in the ballpark of earlier, more conservative estimates based on varied screening eligibility criteria using data from cohort studies (estimated 17.9%– 28.5%).^6,7

The eligibility criteria for Australia’s screening program preferentially select individuals who currently smoke. We report that more than seven in 10 people who will be eligible for lung screening would also benefit from smoking cessation support.

These estimates are subject to several caveats and limitations. They do not account for other screening exclusions, such as symptoms suggestive of lung cancer, or smoking-related mortality, so the true number of people eligible is likely to be somewhat fewer than the estimates presented here. Moreover, the prediction intervals account for uncertainties relating to missing data and model parameters, but not for uncertainty in the choice of modelling approach. Finally, eligibility for and attendance to screening may vary by demographic and social characteristics, which may be of interest for monitoring and evaluation of the program. Future work can extend the methods to address these limitations.

To help evaluate state-and territory-based resource requirements for the program, these estimates can be used to model a range of key performance indicators observed in the screening programs of other jurisdictions (e.g., Canada⁸, UK⁹, USA¹⁰) such as anticipated screening participation and adherence rates, as well as the resource implications for nodule management, actionable incidental findings, smoking cessation support, and lung cancer diagnoses. These estimates can also be used as an indicative denominator to track participation rates for the program over time.