Rapid Fire Best of the Best Oral Clinical Oncology Society of Australia Annual Scientific Meeting 2023

Correlation of Quantitative Emphysema and Lung Nodules on Low-dose CT (LDCT) in the Sydney Cohort of International Lung Screening Trial (ILST) (#214)

Wing Kwan Winky Lo 1 2 , Katrina Tonga 1 2 3 , XinXin Hu 2 , Christopher Rofe 1 4 , Elizabeth Silverstone 5 , Brad Milner 5 , Eugene Hsu 5 , Duy Nguyen 5 , Ian Yang 6 7 , Henry Marshall 6 7 , Annette McWilliam 8 9 , Fraser Brims 10 11 , Renee Manser 12 13 14 , Kwun M Fong 6 7 , Emily Stone 1 2 15
  1. St Vincent’s Clinical School, University of New South Wales, Sydney, NSW, Australia
  2. Department of Respiratory Medicine, St Vincent's Hospital, Sydney, NSW, Australia
  3. Northern Clinical School, University of Sydney, Sydney, NSW, Australia
  4. Kids Cancer Centre, Sydney Children’s Hospital, Sydney, NSW, Australia
  5. Department of Medical Imaging, St Vincent’s Hospital, Sydney, NSW, Australia
  6. Department of Thoracic Medicine, The Prince Charles Hospital, Brisbane, QLD, Australia
  7. Thoracic Research Centre, University of Queensland, Brisbane, QLD, Australia
  8. Department of Respiratory Medicine, Fiona Stanley Hospital, Perth, WA, Australia
  9. Faculty of Health and Medical Sciences, University of Western Australia, Perth, WA, Australia
  10. Department of Respiratory Medicine, Sir Charles Gairdner Hospital, Perth, WA, Australia
  11. Curtin Medical School, Curtin University, Perth, WA, Australia
  12. Department of Respiratory and Sleep Medicine, Royal Melbourne Hospital, Melbourne, VIC, Australia
  13. Department of Medicine (RMH), The University of Melbourne, Melbourne, VIC, Australia
  14. Department of Internal Medicine, Peter MacCallum Cancer Centre, Melbourne, VIC, Australia
  15. The Kinghorn Cancer Centre, Sydney, NSW, Australia

Background and Aims

Low-dose computed tomography (LDCT) imaging for lung cancer screening can detect nodules and emphysema. The association between lung nodules and emphysema is unknown. We aimed to evaluate the relationship between severity of emphysema and presence of lung nodules ≥3mm in the NSW, Australia cohort of the International Lung Screening Trial (ILST).

 

Methods

Candidates who met lung cancer screening criteria for the ILST had baseline LDCT chest and spirometry performed. Lung nodules were evaluated using the PanCan protocol. Emphysema was quantified using standardised threshold of -950 Hounsfield Units (CT COPD, Philips Healthcare). Emphysema extent was calculated as the ratio between emphysema volume and lung volume (% low attenuation area, LAA). Emphysema severity was determined by %LAA thresholds of ≤1%, between 1%-5% and >5%. Chi-square tests assessed for differences between the %LAA groups. Multiple linear regression assessed for predictors of lung nodules ≥3mm.

 

Results

A total of 307 participants (48.5% male, 98% Caucasian) were included (mean±SD: age 64.4±6 years, smoking history 47.4±20.6 pack-years, BMI 27.5±5.2 kg/m2, forced expiratory volume in 1s/forced vital capacity (FEV1/FVC) 0.74±0.08). Median %LAA was 2.03 (IQR 0.62-4.36%). Most participants had %LAA between 1-5% (%LAA ≤1% n=103, 1-5% n=134, >5% n=70). In the group with the greatest amount of emphysema (%LAA >5%) participants were mostly male (n=65.7%, p=0.004), older (66.1±6.0 years, p=0.01), had higher smoking pack-years (51.8±25.0 years, p<0.0001), lower BMI (25.3±4.4 kg/m2, p<0.0001) and most had spirometric airflow obstruction (FEV1/FVC<0.7) (n=58.6%, p<0.0001). Independent predictors of lung nodules ≥3mm were the presence of micro-nodules and emphysema extent (p<0.05).

 

Conclusion

In the NSW ILST Cohort, cross-sectional analysis of LDCT suggests that quantifying emphysema and detection of lung micro-nodules predicts presence of lung nodules ≥3mm. Emphysema severity appeared more extensive in older men, with greater smoking history, and lower BMI. Further longitudinal analysis is needed to determine whether the location of emphysema relative to nodules is important.