Lung Cancer in Never Smokers: Rising Cases, Causes & Early Detection Strategies

Lung cancer diagnoses are rising among people who have never smoked, prompting researchers to investigate the distinct biological factors at play and explore fresh strategies for early detection and prevention. While lung cancer remains overwhelmingly linked to tobacco apply, this growing subset of cases presents unique challenges to traditional screening and treatment approaches.

Globally, lung cancer is the leading cause of cancer-related death, with 2.2 million new cases diagnosed annually, according to recent data. However, the incidence of lung cancer in never smokers (LCINS) is increasing, particularly among women and individuals of Asian descent. This trend is prompting a re-evaluation of risk factors and diagnostic protocols.

Researchers are finding that LCINS often exhibits different molecular characteristics than smoking-related lung cancer. LCINS tumors tend to have a lower mutational burden but a higher prevalence of specific genetic driver mutations. This can impact treatment response, with LCINS patients sometimes showing reduced responsiveness to immune checkpoint inhibitors, a common immunotherapy approach.

Genetic predisposition is emerging as a key factor in LCINS. Variations in genes like EGFR, TP53, ATM, and those within the APOBEC3 family have been linked to increased risk. Certain EGFR mutations, such as p.Thr790Met (T790M), are associated with a particularly high lifetime risk and can lead to the development of multiple lung lesions. Population-specific genetic factors, like deletions in the APOBEC3A/B genes, can significantly elevate risk in certain ethnic groups, suggesting a potential role for genetic screening in high-prevalence populations.

Beyond inherited genetics, acquired biological predispositions are also under scrutiny. Clonal hematopoiesis of indeterminate potential (CHIP), characterized by somatic mutations in blood stem cells, is increasingly recognized as a risk factor for various cancers, including lung cancer, even in non-smokers. Mutations in genes like DNMT3A, TET2, and ASXL1 are commonly found in CHIP, and individuals with high variant allele fractions may face an elevated cancer risk. The mechanism appears to involve chronic inflammation and elevated interleukin-1β (IL-1β) signaling, though the effectiveness of anti-IL-1β therapies remains uncertain.

Environmental exposures also play a significant role in LCINS development. Radon exposure, particularly in indoor environments, is a well-established carcinogen. Air pollution, specifically fine particulate matter (PM2.5), is strongly associated with lung cancer incidence, correlating with increased mutation burden, TP53 mutations, and inflammation. Second-hand smoke exposure increases risk by approximately 20-25%, and tumors in these individuals may exhibit different mutational signatures than those found in active smokers, suggesting a complex interplay of factors.

Current lung cancer screening guidelines, based on low-dose computed tomography (LDCT), are primarily designed for heavy smokers. Applying these guidelines to never smokers is challenging due to the lower baseline incidence and difficulty in identifying high-risk individuals. A clinical trial in Taiwan showed promising results among never smokers with a first-degree family history of lung cancer, leading to an expansion of national screening criteria. However, large-scale randomized trials are needed to assess the mortality benefit and cost-effectiveness of LDCT screening in broader never-smoker populations.

Emerging multi-cancer early detection blood tests, which analyze circulating tumor DNA, are also being investigated, but their sensitivity for detecting early-stage lung cancer remains limited. Researchers are also exploring preventative strategies, including targeted therapies, immunotherapies, and cancer vaccines, with a particular focus on vaccines targeting clonal neoantigens and peptide-based approaches. The high prevalence of actionable driver mutations in LCINS tumors makes this population potentially well-suited for vaccine-based interception strategies.

The increasing burden of LCINS necessitates a shift towards more tailored diagnostic, screening, and therapeutic approaches. Integrating genetic susceptibility, clonal hematopoiesis, family history, and environmental exposures into comprehensive risk models may enable more precise screening and prevention efforts. Further research is crucial to fully understand the biological underpinnings of LCINS and develop effective interception strategies to reduce mortality in this growing patient population.