| Background The outcome among
patients with clinical stage I cancer that is detected on
annual screening using spiral computed tomography (CT) is
unknown.
Methods In a large collaborative
study, we screened 31,567 asymptomatic persons at risk
for lung cancer using low-dose CT from 1993 through 2005,
and from 1994 through 2005, 27,456 repeated screenings
were performed 7 to 18 months after the previous screening.
We estimated the 10-year lung-cancer–specific survival
rate among participants with clinical stage I lung cancer that
was detected on CT screening and diagnosed by biopsy,
regardless of the type of treatment received, and among
those who underwent surgical resection of clinical stage
I cancer within 1 month. A pathology panel reviewed the
surgical specimens obtained from participants who
underwent resection.
Results Screening resulted in a
diagnosis of lung cancer in 484 participants. Of these
participants, 412 (85%) had
clinical stage I lung cancer, and the estimated
10-year survival rate
was 88% in this subgroup (95% confidence interval [CI],
84 to 91). Among the 302 participants with clinical stage
I cancer who underwent surgical resection within 1 month
after diagnosis, the survival rate was 92% (95% CI, 88 to
95). The 8 participants with clinical stage I cancer who
did not receive treatment died within 5 years after
diagnosis.
Conclusions Annual spiral CT
screening can detect lung cancer that is curable.
In 1993, the Early Lung Cancer
Action Project (ELCAP) initiated a study of the early
diagnosis of lung cancer in cigarette smokers with the
use of annual screening with spiral computed tomography
(CT). The principal finding was that
more than 80% of persons
given a diagnosis of lung cancer as a result of annual CT
screening had clinical stage I cancer. This result
has been confirmed by others
who have adopted the updated protocol.
The question remains, however, whether
early intervention in such patients is sufficiently
effective to justify screening large asymptomatic
populations who are at risk for lung cancer. We report the
results of all patients in the study with stage I lung cancer
detected with the use of spiral CT screening, including those
who underwent surgical resection.
In making decisions about instituting CT
screening for lung cancer, a major consideration is the
outcome of treating a cancer detected on screening. In
our study, the estimated 10-year lung-cancer–specific
survival rate among the 484 participants with disease diagnosed
on CT, regardless of the stage at diagnosis or type of
treatment (including no treatment), was 80%.
Among the 412 participants with clinical stage I lung cancer
— the only stage at which cure by surgery is highly likely
— the estimated 10-year survival rate was 88% (95% CI,
84 to 91), and among those with clinical stage I lung cancer
who underwent surgical resection within 1 month after the
diagnosis, the rate was 92% (95% CI, 88 to 95). The
diagnosis of lung cancer of one type or another was
verified by a panel of five expert pulmonary
pathologists. In our series,
the operative mortality rate was low — 0.5% — and was
less than the 1.0% reported with lobectomy in a large
cooperative study.
Sobue reported a 5-year survival rate
of 100% in their series of 29 patients who underwent
resection after pathological stage I cancer was detected
on CT. Before CT screening, reports based on registries
showed 10-year survival rates of 80% among 17 patients
with pathological stage I lung cancer 20 mm or less in
diameter
and 93% among 35 patients with pathological stage
I cancer less than 10 mm in diameter. The National Cancer
Institute's Surveillance, Epidemiology, and End Results (SEER)
registry, the largest U.S. cancer registry, reported an 8-year
survival rate of 75% among patients with pathological stage
I cancer with nodules less than 15 mm in diameter who had
undergone resection.
Although the lung cancers in these three series
were not detected on CT screening, most were presumably incidentally
detected on imaging performed for other reasons in people who
had no symptoms of lung cancer.
CT screening according to the I-ELCAP
regimen can detect clinical stage I lung cancer in a high
proportion of persons when it is curable by surgery. In a
population at risk for lung cancer, such screening could
prevent some 80% of deaths from lung cancer. In
comparison, in the United States at present, annually approximately
173,000 persons are diagnosed with lung cancer and 164,000
deaths are attributed to this disease, so that
approximately 95% of those who are diagnosed with lung
cancer die from it.
Are these results sufficiently
effective to justify screening people who are at risk of
lung cancer? As compared with mammographic screening for
breast cancer, for lung cancer the
rates of detection
among the participants in this study who were 40 years of age
and older were 1.3% on baseline CT screening and 0.3% on
annual screening, values that were slightly higher than
those for the detection of breast cancer (0.6 to 1.0% on
baseline screening) and similar to those for annual
screening (0.2 to 0.4%) among women 40 years of age and
older.
The rate of cancer detection depends on the
risk profile of those undergoing screening; the higher
the risk, the more productive the screening. Thus, as
expected, CT screening of the original participants in ELCAP,
who were former and
current smokers 60 years of age and older,was more productive in
detecting lung cancer (detection rates, 2.7% on baseline
screening and 0.6% on annual screening) than among
participants in the expanded study. The cost of low-dose
CT is below $200,
and surgery for stage I lung cancer is less
than half the cost of late-stage treatment.
Using the original ELCAP data and the actual
hospital costs for the workup, we found CT screening for
lung cancer to be highly cost-effective.
Other estimates of the
cost-effectiveness of CT
screening for lung cancer for various risk profiles are
similar to that for mammography screening. |