The Clinical Value of Pre-Diagnostic Thrombocytosis for the Detection of Lung Cancer in Primary Care

Simple Summary Thrombocytosis, an elevated platelet count, may suggest a patient has an undiagnosed lung cancer. This primary care study analysed data from English electronic medical records linked to the national cancer registry to understand how often thrombocytosis occurs before a lung cancer diagnosis, whether it is a feature of all the different subtypes of lung cancer, and its relation to the cancer's stage at diagnosis. We found that the patients with lung cancer were nearly nine times more likely to have thrombocytosis before diagnosis compared to those without cancer. This association was strongest for squamous cell lung cancer. Thrombocytosis was linked to advanced stages of adenocarcinoma and squamous cell carcinoma, but it appeared equally in both the early and advanced stages of small-cell lung cancer. Thrombocytosis is a risk marker for lung cancer in primary care. We investigated whether thrombocytosis presents pre-diagnostically for all the histological subtypes of lung cancer and its association with the stage at diagnosis. A matched cohort study used English electronic primary care data linked to the national cancer registry. Patients diagnosed with lung cancer aged >= 40 years with no prior history of malignancy were matched by age, sex, and general practice to five controls without lung cancer. Multivariable logistic regression models quantified the incidence of pre-diagnostic thrombocytosis and advanced-stage diagnoses, adjusting for COPD diagnosis, smoking status, and anti-platelet drug prescriptions. A total of 9504 cases were matched to 45,647 controls, consisting of 3260 (34%) adenocarcinomas (ADC), 2020 (21%) squamous cell carcinomas (SCC), 70 (<1%) large-cell carcinomas (LCC), and 1089 (12%) small-cell lung cancers (SCLC). The patients with lung cancer were 8.9 (95% CI 8.0-9.9) times more likely to exhibit pre-diagnostic thrombocytosis than the controls. The odds ratios were highest for the comparison between SCC and ADC (1.8, 95% CI 1.5-2.1). Thrombocytosis is associated with advanced-stage ADC and SCC but presented equally for early- and advanced-stage SCLC. Pre-diagnostic thrombocytosis may aid in the detection of all the histological subtypes in primary care.