Monday, August 16, 2021

Using risk calculators in lung cancer screening discussions

As readers may recall, I changed my mind on lung cancer screening last year and have been working on incorporating screening discussions into visits with eligible patients in my clinical practice. The American Academy of Family Physicians recently endorsed the U.S. Preventive Services Task Force (USPSTF)'s 2021 recommendation to offer annual lung cancer screening with low-dose computed tomography (LDCT) to adults aged 50 to 80 years with at least a 20 pack-year smoking history who have smoked within the past 15 years. Although a meta-analysis of 8 randomized controlled trials found that people screened with LDCT are 19% less likely to die from lung cancer (NNS = 250), it also concluded that about 20% of tumors are overdiagnosed, in line with a previous report from the U.S. National Lung Screening Trial. Unfortunately, doctors do not often discuss harms of lung cancer screening such as overdiagnosis, overtreatment, and complications of diagnostic procedures performed for positive tests.

Deciding if the potential benefits outweigh the harms of lung cancer screening for an individual patient requires a way to personalize estimates of benefit based on patients' risk factors. In a Letter to the Editor regarding a 2019 American Family Physician article on the pros and cons of lung cancer screening, Dr. Abbie Begnaud and colleagues suggested:

If an eligible patient is reasonably healthy, clinicians could consider calculating individualized lung cancer risk using one of several well-validated risk models. We and others have developed web-based tools to help clinicians incorporate individualized risk calculations into decision-making. Individualized risk assessment can be helpful because patients at higher risk of developing lung cancer are also more likely to benefit from early detection through screening. When lung cancer risk increases, uncertainty about whether to recommend screening decreases when the person has a reasonable life expectancy.

Unlike risk prediction tools for cardiovascular disease and breast cancer, however, there is no consensus on which lung cancer risk calculator should be used. A systematic review published earlier this year in the Journal of General Internal Medicine identified 10 publicly available risk calculators and assessed their performance in 16 hypothetical patients across the continuum of lung cancer risk. The calculators used varying inputs (demographic factors, cancer history, smoking status, and personal and environmental factors) to generate lung cancer risk estimates; unsurprisingly, there were substantial differences in risk estimates for 10 of the 16 hypothetical patients. The authors concluded that the lack of standardization of lung cancer risk factors and consistency in risk estimates from web-based calculators may be an obstacle to shared decision making.

Notably, the USPSTF statement "recommends using age and smoking history to determine screening eligibility rather than more elaborate risk prediction models because there is insufficient evidence to assess whether risk prediction model–based screening would improve outcomes relative to using the risk factors of age and smoking history for broad implementation in primary care." In a Putting Prevention Into Practice case study in the July issue of AFP, Drs. Howard Tracer and James Pierre explained how to apply the Task Force recommendations in clinical practice. It will be interesting to see if the Centers for Medicare and Medicaid Services decides to follow the USPSTF and waive its current requirement for a shared decision-making visit prior to lung cancer screening.