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