Association of Weight Loss in Ambulatory Care Settings With First Diagnosis of Lung Cancer in the US.

Importance: Lung cancer, the US's leading cause of cancer death, is often diagnosed following presentation to health care settings with symptoms, and many patients present with late-stage disease. Objective: To investigate the association between weight loss and subsequent diagnosis of incident lung cancer in an ambulatory care population and to assess whether recorded weight change had higher odds of lung cancer diagnosis than objective measurements. Design, Setting, and Participants: This case-control study included patients visiting a US academic medical center between January 1, 2012, and December 31, 2019. Data were derived from US ambulatory care electronic health records from the University of Washington Medical Center linked to the local Surveillance, Epidemiology, and End Results cancer registry. Cases were identified from patients who had a primary lung cancer diagnosis between 2012 and 2019; controls were matched on age, sex, smoking status, and presenting to the same type of ambulatory clinic as cases. Data were analyzed from March 2022 through January 2023. Exposure: Continuous and categorical weight change were assessed. Main Outcomes and Measures: Odds ratios estimating the likelihood of a diagnosis of lung cancer were calculated using univariable and multivariable conditional logistic regression. Results: A total of 625 patients aged 40 years or older with a first primary lung cancer diagnosis and 4606 matched controls were included (1915 [36.6%] ages 60 to 69 years; 418 [8.0%] Asian, 389 [7.4%] Black, 4092 [78.2%] White). In unadjusted analyses, participants with weight loss of 1% to 3% (odds ratio [OR], 1.12; 95% CI, 0.88-1.41), 3% to 5% (OR, 1.36; 95% CI, 0.99-1.88), or 5% to 10% (OR, 1.23; 95% CI, 0.82-1.85) over a 2-year period did not have statistically significantly increased risk of lung cancer diagnosis compared with those who maintained a steady weight. However, participants with weight loss of 10% to 50% had more than twice the odds of a lung cancer diagnosis (OR, 2.27; 95% CI, 1.27-4.05). Most categories of weight loss showed significant associations with an increased risk of lung cancer diagnosis for at least 6 months prior to diagnosis. Patients who had weight loss both recorded in clinicians' notes and measured had higher odds of lung cancer compared with patients who had only recorded (OR, 1.26; odds; 95% CI, 1.04-1.52) or measured (OR, 8.53; 95% CI, 6.99-10.40) weight loss. Conclusions and Relevance: In this case-control study, weight loss in the prior 6 months was associated with incident lung cancer diagnosis and was present whether weight loss was recorded as a symptom by the clinician or based on changes in routinely measured weight, demonstrating a potential opportunity for early diagnosis. The association between measured and recorded weight loss by clinicians presents novel results for the US.