Clinical features of patients with non-metastatic lung cancer in primary care: a case-control study

BACKGROUND: Lung cancer (LC) kills more people than any other cancer globally, mainly due to the late stage of diagnosis. AIM: To identify and quantify the prediagnostic features of non-metastatic lung cancer (nMLC) and to compare the clinical features in GPs’ chest X-ray referral letters with the clinical features (expressed as diagnostic codes) in medical records. DESIGN & SETTING: A population-based case-control study was conducted using diagnostic codes from national and regional healthcare databases in Sweden. METHOD: In total, 373 patients diagnosed with LC in 2011 (of which 132 had nMLC) and 1472 controls were selected from the Swedish Cancer Register (SCR) and regional healthcare database, respectively. Diagnostic codes registered in medical records from primary care consultations in the year before LC diagnosis were collected from the regional healthcare database. Odds ratios (OR) were calculated for variables associated with nMLC. The GPs’ referral letters for chest X- ray were retrieved from the regional repository for radiology. RESULTS: Clinical features with the highest OR were vitamin B12 deficiency anaemia (OR 6.7, 95% confidence interval [CI] = 1.6 to 27.9), dyspnoea (OR 5.0, 95% CI = 2.0 to 12.7), and chronic bronchitis (OR 5.0, 95% CI = 1.3 to 18.6). Clinical features that were GPs’ reasons for requesting chest X-ray were almost three times more frequent in referral letters compared to the corresponding diagnostic codes in the medical records. CONCLUSION: Patients with nMLC could not be identified by symptoms. The clinical features in referral letters for X-ray were more frequent than corresponding diagnostic codes from medical records.