General Practice chest x-ray rate is associated with earlier lung cancer diagnosis and reduced all-cause mortality: a retrospective observational study.

Background: Evidence on whether general practice rates of investigation in symptomatic patients using chest x-ray (CXR) affects outcomes is equivocal.

Aim: Determine if there is an association between rates of general practice (GP) requested CXR and lung cancer outcomes.

Design and setting: Retrospective observational study (England) Methods: Cancer registry data for patients diagnosed with lung cancer 2014-2018 was linked to data on GP CXRs 2013-2017. Stage at diagnosis (I/II vs III/IV) and one and five year survival (conditional on survival to one year) following diagnosis was reported by quintile of CXR rate of patients' GP with adjustment for population differences (age, smoking, prevalence of COPD and heart failure, ethnicity and deprivation) and by unadjusted category (low, medium, high).

Results: 192,631 patient records and CXR rates for 7,409 practices were obtained. Practices with highest quintile CXR rate had fewer cancers diagnosed at stage III/IV compared to lowest quintile (OR=0.87, 95% CI 0.83-0.92, p<0.001). The association was weaker for high unadjusted CXR category (OR=0.94, 95% CI 0.91-0.97). For the highest adjusted quintile HRs for death within one year and five years were 0.92 (0.90-0.95), p<0.001) and 0.95 (95% CI 0.91-0.99, p=0.023) respectively. For the high unadjusted CXR category the HR for one year survival was 0.98 (95% CI 0.96-0.99, p=0.004) with no association demonstrated for five year survival.

Conclusions: Patients registered at GPs with higher CXR use have a favourable stage distribution and slightly better survival. This supports use of CXR in promoting earlier diagnosis of symptomatic lung cancer in general practice.