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I. Imaging of Lung Cancer
II. Authors
James G. Ravenel, MD
Department of Radiology
Gerard A. Silvestri, MD, FCCP
Division of Pulmonary and Critical Care Medicine
Medical University of South Carolina
KEY POINTS:
ISSUES:
1.
Overview
2.
Lung cancer screening:
A. Chest X-ray
B. Computed Tomography
Will CT screening be cost-effective?
3.
Staging of lung cancer
A. Assessment of primary tumor
B. Mediastinal Disease
C. Distant Metastases
Special case: Small Cell Lung Cancer
Special case: Follow-up of Lung Cancer
IV KEY POINTS:
- Screening with chest radiographs does not decrease disease specific lung cancer mortality.
(MODERATE EVIDENCE)
- CT scan is able to detect lung cancers at a smaller size. There is not adequate data to determine
if CT screening is effective in reducing lung cancer deaths. (INSUFFICIENT EVIDENCE)
- CT and PET should be the primary tools for staging non-small cell lung cancer and guiding
invasive studies. (STRONG EVIDENCE)
Issue 1: Is there a role for imaging in lung cancer screening?
Summary
Screening for lung cancer with chest radiographs has not been shown to reduce lung cancer
mortality. The addition of sputum cytology does not increase the yield of screening. Studies on
CT are currently limited to non-randomized trials and therefore the ability of CT to reduce lung
cancer mortality has not been adequately assessed.
Issue 2: How should lung cancer be staged?
Summary
Current staging of lung cancer usually consists of complementary anatomic and physiologic
imaging by computed tomography and positron emission tomography (PET). Magnetic
resonance (MR) imaging is useful for evaluating local extension of superior sulcus tumors into
the brachial plexus. MR may also be used for imaging the central nervous system and
occasionally to image the liver and adrenal glands. Bone scintigraphy may be used to assess for
osseous metastases. Histologic subtypes including squamous cell, adenocarcinoma and large cell
carcinoma are grouped under the single heading non-small cell carcinoma (NSCLC) due to the
similar treatment and prognosis based on stage. Small cell carcinoma, the fourth major subtype,
is staged separately.
Will CT screening be cost-effective?
The ultimate fate of CT screening for lung cancer rests with the presence or absence of mortality
benefit as well as the magnitude of benefit. Even if a benefit is detected, screening may be costprohibitive for the population as a whole. In the absence of long term results, particularly as it
relates to efficacy and morbidity associated with evaluation of nodules eventually deemed
benign, cost-effectiveness is largely speculative as determined by cost-efficacy analysis. Two
analyses have been wildly optimistic, suggesting that lung cancer screening may cost less than
$10,000 per life year saved. This becomes more apparent when compared with other well
accepted intervention screening strategies such as mammography, hypertension screening in 60
year olds and screening donated blood for HIV, which all result in a cost per life year saved of
approximately $20,000. In general, these studies have not accounted well for follow-up of
indeterminate nodules and the possible harms of the diagnostic algorithms on benign disease.
Two studies try to account for these. In one study, assuming 50% of cancers detected were
localized and accounting for a full range of diagnostic work-up and scenarios presumes a cost
per life year saved ranging from $33,000-48,000. The least optimistic model, assuming a stageshift of 50%, used data from previous trials to account for follow-up procedures, benign biopsies
and non-adherence. Under these circumstances the cost per life year saved was calculated as
$116,000 for current smokers, $558,600 for quitting smokers and $2,322,700 for former
smokers. Thus, the cost effectiveness of lung cancer screening will have a great effect on its
implementation.
Special Case: How is Small Cell Carcinoma evaluated?
Summary
Small cell carcinoma (SCLC) is an aggressive neoplasm of neuroendocrine cell origin with a
distinct biologic behavior and is therefore grouped separately from NSCLC. Staging is
determined by a two stage system developed by the Veterans Administration Lung Cancer Study
Group. Limited stage disease includes disease confined to the chest and supraclavicular nodes
that can be contained within a single, tolerable radiation port. For example, small cell carcinoma
with bilateral paratracheal and unilateral supraclavicular adenopathy could be contained within a
reasonable, single radiation port. On the other hand, a pleural effusion would require, in theory,
including the entire hemithorax within a radiation port and encompass too large a field.
Extensive stage disease includes all lesions not characterized as limited stage and those with
distant metastases. Staging strategies for SCLC are similar to NSCLC. Due to the high
incidence of brain metastases, routine imaging of the central nervous system is warranted.
Special Case: What is appropriate radiologic follow-up of lung cancer?
Summary
Two issues arise during the follow-up of lung cancer; measurement of tumors to document
response to therapy and what routine follow-up tests are warranted after the completion of first
line therapy. Long axis unidimensional measurements are appropriate for following lesions with
CT or MR. To the extent possible, the same scanning technique and interpreter should follow an
individual case. FDG-PET may eventually provide additional data by following metabolic
response via SUV determination. After definitive therapy, routine imaging evaluations are not
necessary.
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