Independent prognostic value of method of detection in lung cancer: Analysis of the PLCO lung screening trial.

Abstract

e22526 Background: Prognostic models in cancer use patient and tumor characteristics to predict survival and disease progression. Many tumors are detected as part of screening programs such as colonoscopy for colorectal cancer, mammograms for breast cancer, and pap tests for cervical cancer. Past work in breast cancer has shown that screen detected tumors exhibit better prognosis than symptom detected tumors. The prognostic significance of method of detection in other types of cancers is less well understood. Further, the importance of method of detection, relative to other prognostic variables such as sex, age, cancer stage at diagnosis, and histology, is largely unknown. Methods: The prognostic significance of method of detection in the PLCO Lung cancer screening trial was investigated. PLCO randomized patients to intervention, with four annual chest x-ray (CXR) screenings, or control, usual care. Patients were followed for a total of approximately 13 years. All patients diagnosed with non-small cell lung cancer within 4 years of randomization were considered in the analysis (N = 934). Cox proportional hazards model and Random Survival Forests were used to build prognostic models to predict overall survival. The importance of each variable in prognostic models was assessed using hazard ratios and Random Forest variable importance measures. Results: Screen detected tumors exhibit stage shift and have better prognosis than interval and control detected tumors. The improved prognosis remains significant after controlling for stage at diagnosis and other variables commonly used in prognostic models (e.g., age, histology, sex). Variable importance measures show that method of detection is a more important prognostic indicator than sex and histology. Results are robust to different methods for cohort selection. Conclusions: Method of cancer detection should be considered when developing prognostic models in lung cancer studies. Cancer registries should routinely collect method of cancer detection.