Background Overdiagnosis among clinically detected lung cancers likely consists of cases that are non-aggressive and slowly progressive and will never disseminate, cause symptoms or be a threat to a subject’s survival, even if untreated. In this study, we estimate the prevalence of non-aggressive lung cancers from a large, population-based cancer registry.
Methods We identified individuals ≥65 years with histologically confirmed, untreated stage I non-small cell lung cancers (NSCLCs) from the Surveillance, Epidemiology, and End Results-Medicare registry. We estimated the rate of non-aggressive lung cancers by determining the point at which the cumulative lung cancer-specific survival curve no longer changed (ie, the slope approaches zero). At this point, there are no additional deaths due to progressive lung cancer observed among untreated patients after adjusting for deaths from competing risks (these long-term survivors can be considered ‘non-aggressive cases).
Results The overall rate of non-aggressive cancers among 2197 clinically detected cases of untreated stage I NSCLC was 2.4%, 95% CI: 1.0% to 3.8%. The rate of non-aggressive cancer was 1.9% (95% CI: 0.0% to 4.9%) for women and 2.4% (95% CI: 0.7% to 4.1%) for men (p=0.84). When stratifying by tumour size, non-aggressive cancer rates were 10.2% (95% CI: 0.0% to 29.3%), 2.1% (95% CI: 0.0% to 9.2%), 4.9% (95% CI: 0.0% to 10.3%), 1.8% (95% CI: 0.0% to 5.2%) and 0.0% (95% CI: 0.0% to 1.0%) for tumour sizes <15 mm, 15–24 mm, 25–34 mm, 35–44 mm and ≥45 mm, respectively. In comparison with the smallest tumour sizes (<15 mm), the rates of non-aggressive cancers were not statistically significantly different for tumour sizes 15–24 mm (p=0.36), 25–34 mm (p=0.57), 35–44 mm (p=0.38) and tumour sizes >45 mm (p=0.30).
Discussion We found relatively low rates of non-aggressive cancers among clinically detected, stage I NSCLC regardless of sex or size. Our findings suggest that most clinically diagnosed early stage cancers should be treated with curative intent.
- non-small cell lung cancer
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Contributors Study concept and design: MSK, KS and JPW. Acquisition, analysis or interpretation of data: MSK, GM, KS and JPW. Drafting of the manuscript: MSK. Critical revision of the manuscript for important intellectual content: GM, KS and JPW.
Competing interests JPW is a member of the research board of EHE International, has received consulting honorarium from Quintiles, AstraZeneca and Merck and a research grant from Aventis Pharmaceutical and Quorum. KS has received honorarium from Gilead.
Ethics approval Icahn School of Medicine Institutional review board.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement MSK had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
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