# Evaluation of the safety of short-term follow-up CT for the management of consolidation in lung cancer screening

## TL;DR

Short-term CT follow-up for lung cancer screening is safe and cost-effective, reducing unnecessary tests by showing that many consolidations resolve on their own.

## Contribution

Demonstrates the safety and cost-effectiveness of short-term CT follow-up for managing consolidation in lung cancer screening.

## Key findings

- Over 50% of participants showed spontaneous resolution of consolidation after 6 weeks.
- Persistent consolidation had a high likelihood of malignancy (12.7%).
- No patients experienced upstaging during the 6-week follow-up period.

## Abstract

Focal consolidation on CT may be inflammatory or malignant, and PET-CT imaging is rarely discriminatory. Furthermore, consolidation may demonstrate spontaneous resolution obviating the need for PET-CT imaging. This retrospective study sought to assess the safety and cost-effectiveness of short-interval 6-week follow-up CT for consolidation in a lung cancer screening programme.

Between January 2019 and January 2024, participants in a regional lung cancer screening programme with focal indeterminate consolidation underwent a 6-week repeat CT rather than immediate PET-CT and invasive investigation. The proportion of participants with non-resolving consolidation, the risk of malignancy in consolidation at a 6-week follow-up, and the risk of upstaging over a 6-week delay were determined. Cost savings were estimated from National Health Service reference costs.

In 10,247 CT studies, focal indeterminate consolidation was detected in 113 participants (1.1%) (mean age 68 years, range 55–76, 65 males). Consolidation spontaneously resolved at 6 weeks in 63/110 (57%) who attended follow-up; 14/110 (12.7%) participants had malignancy; no patients upstaged during follow-up. An estimated cost saving of £47,600/10,000 screening CTs performed might be obtained through a conservative approach of short-term interval CT, rather than immediate PET-CT and further investigation.

Early repeat CT avoids PET-CT in more than half of patients with consolidation and can be utilised to reduce over-investigation of screen-detected consolidation, which may demonstrate spontaneous resolution.

Question
Is short-term interval follow-up CT in lung cancer screening a safe and cost-effective approach to managing indeterminate (inflammatory or malignant) consolidation?

Findings
Short-interval CT imaging demonstrates spontaneous resolution of consolidation in over 50% participants in this study, whilst persistent consolidation has a high likelihood of malignancy.

Clinical relevance
Short-interval CT did not result in upstaging of malignancy and therefore can be considered a safe strategy to prevent the over-investigation of screen-detected consolidation, supporting recent European and American screening recommendations.