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Most patients found to have lung
cancer die within a year largely because their tumor has already spread, making
treatment difficult. Now there is real reason to believe that lung cancer can
be detected early and with it witness an improvement in cure. Given that
160,000 Americans die each year - more than the next four cancers combined – early
diagnosis followed by curative treatment would be a major advance.
For many years it was considered
useless to screen individuals for lung cancer with chest x-rays in a manner
comparable to mammography for breast cancer, PAP smears for cervical
cancer or colonoscopy for colon cancer
because a chest X-ray only detected lung cancer when it was far advanced, which
rarely meant detecting a cancer that could be cured. Over the past decade it
has been postulated that CT scanning could detect lung cancer while it was
still small and localized. Now as a result of careful randomized controlled
studies, low dose CT (LDCT) scanning has proven effective in screening for lung cancer in
high-risk populations.
The largest LDCT study, the National Lung
Screening Trial or NLST, was sponsored by the National Cancer Institute.
Between 2002 and 2004 some 53,454 individuals were randomly allocated to be
screened annually for three years with either routine chest X-ray or with low
dose CT scans with data collected through the end of 2009. The screening criteria were high-risk
individuals, i.e., between the ages of 55-74,
current or former smoker, 30+ pack years and still smoking until at least 15
years before. The results suggest that not only can early lung cancer be
detected by LDCT but also that mortality can be reduced.
For each annual scan, about twenty of
every 100 (20 percent) of individuals will be found to have a nodule. But only one
patient of every 100 will have lung cancer; that is only 5 percent (one of 20)
of those with a nodule will be due to cancer, the other 19 of the twenty
nodules (95 percent) are benign. To establish which are cancer and which are
not, the next step is to follow the nodule with repeat CT scans or to do a
biopsy.
In an effort to avoid an invasive
procedure to obtain the biopsy, the usual approach was to schedule repeat scans
at three or six month intervals. Many individuals were given a scare before
they were told all was okay many months or a year later when the repeat CT
scans showed that the lesion either was stable or disappeared.
The value of screening was demonstrated by
the observation that 63% of cancers detected by LDCT were Stage IA or IB,
distinctly different from the norm where most are found at advanced stages. When
cancer was found, surgical resection with or without adjuvant chemotherapy or
radiation therapy was the usual treatment. Overall, deaths from lung cancer
were reduced by about 20% by using the LDCT scanning as described compared to
chest X-ray screening.
A few examples of false positives are
illustrative of the dilemma:
A middle aged lady who had quit smoking
ten years before was attracted by an offer at a local hospital to be scanned
for only $75. She got a letter in the mail some weeks later saying she had a very
small nodule that required follow-up. Naturally she was upset. Six months later
she had another CT. At that screening she was told her scan was normal but that
she should get screened again in six months “just to be on the safe side.”
Ultimately she chose not to have any additional screening and remains fine
albeit having had a tortuous path.
Another lady had a similar experience. Her nodule was larger and she had a year of every 3 months getting a CT scan and then after a year, every 6 months for two years at which point she was told that it was likely not cancer but that she should continue screening for another year. She has remained disease free.
An elderly gentleman with chronic lung disease who had been a heavy smoker for over 30 years had a lung nodule detected on CT scan. He was told it was highly suspicious for cancer. He had surgery to establish the diagnosis resulting in a collapsed lung with a difficult recovery. The pathology showed that the nodule was not cancer but rather histoplasmosis in need of no therapy.
Another lady had a similar experience. Her nodule was larger and she had a year of every 3 months getting a CT scan and then after a year, every 6 months for two years at which point she was told that it was likely not cancer but that she should continue screening for another year. She has remained disease free.
An elderly gentleman with chronic lung disease who had been a heavy smoker for over 30 years had a lung nodule detected on CT scan. He was told it was highly suspicious for cancer. He had surgery to establish the diagnosis resulting in a collapsed lung with a difficult recovery. The pathology showed that the nodule was not cancer but rather histoplasmosis in need of no therapy.
It is this high false positive rate that
raises questions of risk benefit and cost effectiveness. The opportunity
for early diagnosis of lung cancer raises important issues. The NLST studied
only older individuals with a long and heavy smoking history, i.e., those at
highest risk. For those, over 20 percent were found to have a pulmonary lesion
of which 1 in 20 were ultimately found to be cancer. And those who were
screened with CT scanning ultimately had a 20% reduction in lung cancer
mortality compared to those screened with regular chest X-rays. If the
screening criteria were loosened to include a broader base (as in the hospital
above that offered inexpensive screening for any current or former smoker),
would the result still be a high lesion discovery but a proportionately much
smaller number of cancers discovered? Whether or not the screening criteria are
expanded, the high rate of non-cancer/benign diagnoses requires careful consideration.
These are individuals who, based on their smoking history, have a high
prevalence of chronic lung disease and possibly cardiac disease, together
making them less amenable to invasive procedures to confirm or eliminate a
cancer diagnosis. As a result, more patients in the study were followed with
repeat CT scans to determine if the lesion progressed – an approach linked to
high stress levels for the individual patient and for the patient’s family.
Clearly, an approach capable of resolving the diagnostic dilemma that is less
invasive than needle biopsy or surgical incision is required. Some new
technologies may soon be forthcoming in this regard.
Taking all of this data into
consideration, many professional societies such as the American Cancer Society,
the American College of Chest Physicians and the American Society of Clinical
Oncology have endorsed offering LDCT scanning for these high-risk individuals
but only provided that there is first a thorough discussion of risks and
rewards between physician and patient.
For now, those who are at high risk
for lung cancer, i.e., the criteria used in the NLST, should consult with their
physician and carefully weigh the pros and cons of screening. Clearly, LDCT can
detect lung cancer and detect it early when treatment options are much better.
But the risks including anxiety related to a positive scan which may be a false
positive are real. If scanning is opted
for, it should only be accomplished at an institution with high levels of
expertise and experience. And should cancer be ultimately detected, it is best
to be treated at an institution that not only has staff with the necessary
expertise and experience but also utilizes the multi-disciplinary approach
where thoracic surgeon, radiation oncologist and medical oncologist all
interact with the patient together and offer a unified plan of care.
The finding that LDCT can detect
lung cancer while it is still small and localized is a major advance. Study
patients were 20% less likely to die of lung cancer compared to those who were
screened with regular chest X-rays. It opens the opportunity for cure with a
combination of surgical resection or radiation therapy plus adjuvant
combination chemotherapy. It also suggests the opportunity to begin, at an
earlier stage, effective treatment for those found to have some overt spread of
disease. Hopefully new non or less invasive yet rapid diagnostic venues will be
shortly brought to bear on differentiating which lesions are cancer and which
are benign.
