Chest x-ray sensitivity and lung cancer outcomes: A retrospective observational study.

BACKGROUND Chest x-ray (CXR) is the first line investigation for lung cancer in many healthcare systems. Understanding of the consequences of false negative CXRs on time to diagnosis, stage and survival is limited. AIMS To determine the sensitivity of CXR for lung cancer and to compare stage at diagnosis, time to diagnosis and survival between those with CXR which detected, or did not detect, lung cancer. DESIGN & SETTING Retrospective observational study using routinely collected healthcare data. METHODS All patients diagnosed with lung cancer in a teaching hospital trust during 2008 - 2015 who had a GP requested CXR in the year before diagnosis were categorised based on the result of the earliest CXR performed in that period. We calculated sensitivity of CXR and performed analyses with respect to time to diagnosis, survival and stage at diagnosis. RESULTS CXR was negative for 18% of patients (n=376/2129). Median time from initial CXR to diagnosis was 43 days (IQR: 27-78) for those with positive CXR and 204 days (105-287) for those with negative CXR. Of those with positive CXR, 29% (95% CIs 27-31%) were diagnosed at either stage I/II, compared to 34% (95% CIs 29-39%) of those with a negative CXR. CONCLUSION GPs should consider lung cancer in patients with persistent symptoms even when CXR is negative. Despite longer duration to diagnosis for those with 'false negative' CXRs, there was no evidence of adverse impact on stage at diagnosis or survival; however this comparison is likely to be affected by confounding variables.