Lung cancer has enjoyed the dubious distinction of occupying the number one spot among cancer killers for some time now, accounting for over a quarter of all cancer deaths yearly for both men and women. Small wonder then that when the results of the National Lung Screening Trial (NLST) were released, showing that low dose CT screening reduced lung cancer deaths by 20%, the news was greeted with elation among clinicians and widespread adoption. Now a study Rick and I discuss on PodMed and published in the New England Journal of Medicine demonstrates that even among smokers and former smokers, low dose CT screening can be targeted more effectively to benefit those most likely to benefit, while avoiding the harms of radiation exposure to those who likely won't be helped by screening.
Investigators in this study used the vast majority of data from the NLST to assess variations in efficacy, the number of false positive results, and the number of lung cancer deaths prevented in the group who had screening CT versus the group who had chest X-rays. These were calculated based on five categories of five year risk of developing lung cancer among study participants, ranging from low to high. Additional factors that accounted for risk stratification included age, body mass index, family history of lung cancer, pack-years of smoking, years since smoking cessation, and diagnosis of COPD. For the model for competing cause of death, family history of lung cancer was eliminated and race and sex were added.
The study determined that as the risk of dying of lung cancer increased, so did the number of deaths averted by utilization of low dose CT screening. Investigators calculated that the number needed to screen in the highest risk group to prevent one lung cancer death was 161, compared to 5276 in the lowest risk group. The ratio of participants with false positive results, a very common problem with this technology to screen for lung cancer, to the number of CT-prevented lung cancer deaths decreased from 1648 to 1 in the lowest risk quintile to 65 to 1 in the highest risk group, clearly indicating the improvement in risk/benefit as the risk of lung cancer death increased.
The study provides abundant evidence for further targeting use of low dose CT to screen for lung cancer to those at highest risk for lung cancer death. As a reminder, subjects who enrolled in the NLST were between the ages of 55 and 74 years, had smoked a minimum of 30 pack years and had quit no more than 15 years previous to beginning the study, so presumably, a high risk group to begin with in whom it may be tempting to recommend global screening. Yet with evidence emerging on the cumulative risk relative to radiation as well as efforts to control healthcare costs, especially as related to screening of all types, this study provides a rationale for a targeted approach. As I conclude on PodMed, any former smoker who is told to have screening CT should consider this study.
Other topics this week include infertility in women who've survived childhood cancer in the Lancet Oncology, aspirin and colorectal cancer prevention in women in Annals of Internal Medicine, and high blood pressure medications, compliance, and stroke risk in the European Heart Journal. Until next week, y'all live well.