CT scan in Early Lung Cancer Detection:
Utility and Pitfalls
Annette McWilliams
30 March 2007
Male Cancer Mortality in Canada
Female Cancer Mortality in Canada
Port, J. L. et al. Chest 2003;124:1828-1833
Disease-specific survival of patients with Stage IA tumours ≤ 2 cm or > 2 cm
Lee P, General Thoracic Surgery Dec 2006;132:1382-1389
Screening with CT
• Large burden of disease • Feasible • Detects cancer at early stage • Early effective treatment possible • Low risks ?
• Reduces deaths from the disease ?
• Cost effective ?
Ongoing Issues
• Utility
- Mortality outcomes
- Much discussion re overdiagnosis/other biases
• Pitfalls
- Risks
- Best management of “false positive ” nodules
Overdiagnosis
• CT pictures of HB
2 years observation
Overdiagnosis
5 months observation
Overdiagnosis
• ↑ BAC vs invasive adenoCA in never cf ever smokers in Japanese data
• Excellent longterm outcomes in pure BAC < 2cm
• Only 1/39 cancers (2.6%) in LHS was non-invasive pure BAC & 7% in I-ELCAP
• All untreated Stage 1 cancers in I-ELCAP died within FU period
Sone 2003
Asamura 2003, Nakamura 2004
Biologically aggressive NSCLC
8mm adenocarcinomaEarly 2002
N3 disease ~ 3 years later
Biologically aggressive NSCLC
Central Lung Cancers
25% cancers in LHS-all CT occult20-75% persistence/progression on short-medium followup
Second Lung Cancers
2002 2005
Limitation of Risks
Procedures/surgery for benign disease
• Only 19% of suspicious lesions had diagnosis before intervention/treatment
• 18-27% surgeries for benign lesions
• 3% of all participants had a TTNA/med/surgery
• 0.9% of all participants had unnecessary procedures (TTNA or surgery)
Radiation Risk
• >80% of lifetime exposure is from background radiation
• Data extrapolated from atomic bomb data and nuclear workers- usually one single exposure
• Difficult to be accurate for exposures <100 mSv
• Linear exposure model used for lower doses• Pronounced age effect• Differing organ radiation sensitivity
Copyright ©Radiological Society of North America, 2003
Mayo, J. R. et al. Radiology 2003;228:15-21
Figure 2. Graph compares lifetime mortality risk from cancer per sievert to age at the time of exposure
Brenner Radiology 2006. Relative risks in atomic bomb survivors
Brenner Radiology 2006. Excess cancer mortality in atomic bomb survivors
Radiation Risks
Dose
Low dose thoracic CT 1.2 mSv
Standard VGH thoracic CT 2.4 mSv
Mammogram 1.5 mSv to breasts
Chest X-ray 0.15 mSv
Background Radiation 3 mSv/year
85% screened subjects will need CT surveillance for 2 years
Radiation Risk
Dose
Low dose thoracic CT 1.2 mSv
3-5 FU thoracic CT over 2 yrs 3.6 – 6 mSv
Annual surveillance 25 years 30 mSv
Radiation Risk
Individual CT dose of 5.2 mSv
Brenner 2004
Pulmonary Nodules
• 85 % screened subjects will have abnormalities requiring surveillance for 2 years
• Majority of nodules are < 5mm
• How do we manage these lesions clinically?
Pulmonary Nodules
Features that influence clinical management:
1. Size
2. Appearance
3. Longitudinal behaviour
Solid (90%) GGO (6%)
SSN (1%) PFO (3%)
High Risk Population 50-74 yo
≥ 30 pack/yearsNo prior lung cancer
N= 1357
Probability of cancer = 2.6%
Positive CT scan3.1%
Negative CT scan0.7%
Pulmonary NoduleProbability of cancer = 0.6%
Nodule < 10mmNodule < 10mmProbability of cancer
= 0.2%
Nodule ≥ 10mmProbability of cancer
= 11.4%
Nodule ≥ 10mmProbability of cancer
= 11.4%
Solid 13.4%
Semisolid40%
Nonsolid4.9%
PFO0%
Nodule < 10mmProbability of cancer
= 0.2%
Solid 0.2%
Semisolid0%
Nonsolid0.5%
PFO0%
Nodule < 10mmProbability of cancer
= 0.2%
Solid 0.2% → 3.9%
Nonsolid0.5% → 13.6%
Growth on 1 Followup CT scan
Nodule < 10mmProbability of cancer
= 0.2%
Solid 0.2% → 3.9% → 50%
Nonsolid0.5% → 13.6% → 50%
Growth on 2 Followup CT scans
PET Imaging for Screening Detected Suspicious lesions
No. Mean diameter
PET
positive
Malignant lesions
18 15mm 39%
Benign Lesions
7 13mm 43%
Sensitivity = 39% Specificity = 57%PPV = 70% NPV = 27%
British Columbia Cancer AgencyStephen Lam
Calum MacAulaySukhinder Khattra
Don Wilson
SupportNCIC, NIH (USA), BC Lung Association
Vancouver General Hospital
John MayoRichard Finley
Ayman Al-SulaimaniKen EvansJohn Yee
John EnglishJulia Flint