Increased use of diagnostic CT imaging increases the detection of stage IA lung cancer: pathways and patient characteristics

BACKGROUND: At Silkeborg Regional Hospital, Denmark, the number of stage IA lung cancer increased after implementation of increased use of CT investigations and a corresponding reduction in chest X-ray. The aim of the present study was to understand the changes in referral pathways, patient characteristics and imaging procedures behind the observed increase in early-stage lung cancer.

METHODS: The referral and imaging pathways for all patients diagnosed with lung cancer in 2013-2018 were described based on manually curated information from the electronic health care systems and staging information from the Danish Lung Cancer Registry. We compared the clinical characteristics of patients diagnosed in 2013-2015 and in 2016-2018 after implementation of a change in the use of low dose CT scan (LDCT). For patients diagnosed in 2016-2018, stage IA lung cancer were compared to higher stages using univariable logistic regression analysis.

RESULTS: Five hundred and forty-seven patients were diagnosed with lung cancer in 2013-2018. Stage IA constituted 13.8% (34/247) in 2013-2015, and 28.3% (85/300) in 2016-2018. Stage IA patients in 2016-2018 were characterised by more comorbidity, fewer packyears and tended to be older than patients with higher stages. In 2016-2018, the largest proportion of stage IA patients (55%) came from within-hospital referrals. The majority of these lung cancers were detected due to imaging procedures with other indications than suspicion of lung cancer. The proportion of stage IA increased from 12% (12/99) to 36% (47/129) (p < 0.001) for hospital referrals and from 17% (22/129) to 23% (38/165) for GP referrals (p = 0.21). The imaging procedures contributing to the increase in stage IA was contrast enhanced CT (22%¸11/51), LDCT (35%; 18/51) and X-ray followed by LDCT (25%; 13/51).

CONCLUSION: The increased access to LDCT for patients referred from general practice and the increased hospital requested CT activity resulted in an increase in the number of stage IA lung cancers. Incidental findings on imaging performed for diagnostic purposes unrelated to suspicion of lung cancer contributed a large proportion of the increase.