Should we screen for lung cancer in Australia?

Lung cancer is the leading cause of cancer death in Australia. Late diagnosis of advanced disease contributes to the poor 13% 5-year survival rate associated with lung cancer. However, the recently updated United States National Lung Screening Trial (NLST) showed a 20% survival benefit from early detection with low-dose computed tomography (CT) screening.1,2 In light of these results, should people in Australia at high risk of lung cancer now undergo screening?

The NLST randomly allocated 53 000 participants to three rounds of annual screening with either chest CT or chest x-ray, with follow-up for a further 3 years.1,2 Unlike population-based screening programs for other common cancers, the NLST only enrolled high-risk participants (ie, current smokers or former smokers who had quit within the past 15 years, aged between 54 and 74 years, with > 30 pack-years). Adherence to screening was over 90%. At the initial screen, three times more stage 1A tumours (< 3 cm, no metastases) were detected on CT than on chest x-ray; most of these were resected.2 However, the absolute reduction in the risk of death from lung cancer was small (0.33%), with 320 participants being screened annually for 3 years to avoid one lung cancer death over 6 years.1

Harm did occur.3 The cumulative positive scan rate approached 40% over 3 years.1 While it is not directly comparable because of different screening intervals, this rate is several times higher than that in other screening programs, such as the Australian National Bowel Cancer Screening program, where only 7.8% of people screened biennially had a positive result on the screening test (faecal occult blood test).4

In the NSLT, over 95% of positive scans were shown to be false positives — that is, cancer was not present. However, most false positives required only repeat scanning. Invasive investigations were needed in a minority of instances, and the risk of fatal complications was small (0.03% within the CT arm of the study), reflecting the expert care provided to participants at trial centres. Radiation-induced cancer death could not be measured in the 6-year follow-up of the NLST, but is estimated at 0.04% 10–15 years after screening at the relevant levels of radiation exposure.3

Lung cancer screening therefore appears efficacious under optimal conditions and in expert hands. The absolute benefit, however, is modest and may be rapidly eroded by small decrements in effectiveness, or minor increments in harm.3 For example, a doubling of radiation risk (with the use of older scanners) and fatal complications (at inexperienced centres) coupled with a halving of screening effectiveness (by a lack of expert treatment pathways) could completely negate all benefit. Therefore, despite ready access to CT scanners, screening should not be performed sporadically in the absence of a systematic screening infrastructure.

Before Australia can embark on systematic screening, issues of local feasibility must be addressed. Many such questions will be answered by the Queensland Lung Cancer Screening Study, which is now midway through recruitment.5 This study adapted the NLST protocol to an Australian population, and will inform the implementation of future screening.

Cost presents a more formidable challenge. Of the approximately two million individuals in Australia aged between 54 and 74, roughly 400 000 were smokers 15 years ago, and many continue to smoke. Not including infrastructure, the cost of a screening program comprising three annual CT scans (with downstream tests and treatments) was calculated at $16.5 million per 10 000 individuals screened (2002 prices).6 Screening 400 000 individuals over 3 years would therefore cost $660 million. Assuming a screening uptake rate of 75%, annual costs would amount to $165 million.

Is such expenditure cost-effective? Dividing $660 million by an estimated 1250 lives saved gives a cost of $530 487 per death averted. Assuming a sustained benefit from screening, each patient whose death from lung cancer is averted gains 13 life-years.7 Thus the cost per life-year gained is in the region of $40 000, which approaches the cost-effectiveness of biennial bowel screening8 or cervical screening.9

However, there is already a more powerful method to reduce mortality in this high-risk population. Primary prevention is far more effective than screening, by at least an order of magnitude. The direct costs of smoking cessation interventions in 2003 Australian prices were between $1000 and $4000 per successful quitter, depending on the combination of cessation techniques.10 The cost of smoking cessation interventions per life-year gained therefore ranges between $250 and $1000, because smoking cessation adds 4 years of life to each quitter in their early sixties.11 Younger quitters derive even greater benefit.11

Formal up-to-date costings for screening should be undertaken given that available Australian models are a decade old. However, national lung screening is likely to strain health care expenditure, already stretched by expansions to breast and bowel screening programs. While systematic screening would likely save some lives, its running costs may be equivalent to the annual expenditure on all lung cancer care.12

In the United States, alternatives to full government support are being suggested, such as partially or fully self-funded screening, or tobacco-taxation. In Australia, the question for debate is whether screening should be implemented at all, until effectiveness and cost-effectiveness are substantially enhanced. Currently, smoking cessation is far ahead on both counts. Thus, greater emphasis (and more funding) should be directed towards intensified tobacco control and sustained quitting.

For now, in the absence of a coordinated nationwide program, we caution that sporadic lung screening has the potential for harm rather than benefit. We propose instead that smokers should be vigorously directed towards quitting.