Spiral CT scanning (more accurately called Helical CT) of the chest is a method of
scanning patients for lung cancer that can detect lung cancers
at an early stage.
Lung cancer is the number one cause of cancer death in
American men and women, killing approximately 160,000 each year.
If the diagnosis is made early (stage I disease), the percentage of those alive five
years after diagnosis 60-80%. Unfortunately, lung
cancers are often not detected until after symptoms appear, when
the lung cancer is already at later stages and the cure rates
are significantly lower. The
percentage alive in five years after a diagnosis of advanced
disease is only 1-13%. Without lung cancer screening, the percentage of
lung cancers
diagnosed with stage I disease is only 15%. In a population of
people screened yearly for lung cancer with CT, the percentage
of cancers
diagnosed with stage I disease rises to 75%.
Five-year survival rates are clearly different for diagnoses
made at different stages. However, there is some ongoing
debate in the medical community and ongoing research as to
whether screening for lung cancer is cost effective and whether
detecting lung cancer at an earlier stage really makes a
difference in overall survival. It is possible that people diagnosed with lung cancer
at an early stage using CT screening will still die at the same time
they otherwise would have, except with a longer lead time
between when they know of their disease and when they die.
Some argue that survival rate at five years after diagnosis is
higher because of "lead time bias." This argument is that
the numbers only seem better because we start counting the five
years at an earlier time, and not because earlier diagnosis lead
to more effective intervention. The
fact that the number of lung cancers diagnosed each year is almost identical to
the number of deaths from lung cancer each year (within 10%), suggests that
almost everyone who gets lung cancer, even those diagnosed with
early stage disease, dies of it.
While it seems intuitively obvious that earlier diagnosis
should allow higher cure rates, the debate will continue for
some time, until more definite long-term followup research data
is available.
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