Lung cancer is a malignancy originating from lung tissue. It is the second most common cancer in men (after prostate cancer) and women (after breast cancer). There are approximately 170,000 new cases each year. Although it is not the most common cancer in either gender, it is the leading cause of cancer deaths in both men and women. Overall cure rates are approximately 15%. Lung cancer is difficult to cure because of the high likelihood of spread outside the lung to other organs. It also can recur in the lung despite treatment.
There is a clear association
of lung cancer with smoking. A person
who smokes one pack/day for 20 years has an approximately 20 times greater risk
of developing lung cancer than a non-smoker. Other
environmental exposures such as radon or asbestos also increase the likelihood
of the developing lung cancer. There are also specific genes which, when
present, can increase the risk of lung cancer.
In-depth
Information
Lung
cancer is divided into two categories: small cell (SCLC) and non-small cell (NSCLC).
NSCLC has three further sub-classifications: squamous cell,
adenocarcinoma, and large cell. The
designation of lung cancer into one of the above categories depends on its
appearance under the microscope as well as cell surface markers. The
most common presenting symptom is cough, being present in 75% of patients
and severe
in 40%. Coughing up blood (hemoptysis)
is present in more than one-half of the patients. Patients can also present with shortness of breath, chest pain,
rib or shoulder pain. Weight loss,
generalized weakness, and loss of appetite occur in approximately 10 to 15% of
the patients. Hoarseness can result
from involvement of the nerve that controls the vocal cords. Secondary tumor effects
(paraneoplastic
syndromes) are also sometimes seen.
Generally, a patient presents to the primary care physician with a concern regarding one of the complaints described above. A careful history and physical examination is the first step in the diagnosis of lung cancer. The most common radiologic examination is a routine chest x-ray. Computed tomography (CT or CAT scan) is the most valuable radiologic study for evaluating lung cancer and its potential spread to the lymph nodes in the chest, to the adrenal glands, or to the liver. It is essential that a piece of the lung cancer be sampled and evaluated by the pathologist to determine whether a mass is cancerous. This usually involves a fiberoptic bronchoscopy where a tube is placed into the patient’s windpipe so that a biopsy of the tumor can be obtained. With this procedure, the bronchoscopist can also obtain washings and brushings of the bronchial tree that can help in the diagnosis of cancer. Sometimes cancer can be diagnosed from tests on a sample of sputum, which is coughed into sputum cups by the patient. Lung cancer tissue may also be obtained by a CT-directed biopsy, depending on the location of the tumor. Blood work will also be performed as a guide to evaluate if the cancer has spread to other organs. For SCLC, a CT or MRI of the brain will often be performed to ensure that the cancer has not spread to the brain. Patients who may be candidates for surgical resection may have other tests such as pulmonary functions tests to evaluate the patient’s ability to undergo surgical resection, mediastinoscopy to evaluate the central chest lymph nodes for potential spread of cancer, or exploratory thoracotomy to evaluate the extent of the tumor in the lung.
The staging of lung carcinoma depends on the tumor size, lymph node involvement, and the presence of metastasis (lung cancer that has spread to other organs).
SCLC can be staged by the above criteria; however,
it is often
described as being extensive stage or limited stage. Limited stage generally means that
all of the cancer can be encompassed in a single reasonable radiation therapy
portal (limited to the
lung) while extensive stage means the cancer has spread to organs outside the
lung.
The treatment of lung cancer is highly dependent on the type—SCLC vs. NSCLC—and the stage at presentation. SCLC has a high likelihood of metastasis to other organs; therefore, the mainstay of treatment is chemotherapy in these patients. For limited stage disease, the patient usually will undergo concurrent chemotherapy and radiation therapy to the chest; patients with a complete response to this treatment usually will then receive prophylactic radiation therapy to the brain to prevent the development of clinical brain metastases. In patients with extensive stage disease, chemotherapy is the main form of treatment; however, radiation therapy may be used to treat organ sites in a palliative manner (control pain or symptoms related to the disease).
In NSCLC, the best hope for cure is
when the cancer can be
resected surgically. Radiation therapy and/or chemotherapy may be recommended
as postoperative treatment based on the findings at surgery. In patients who are not surgical candidates
and have no spread of the disease to other organs, radiation therapy to the
chest and chemotherapy are recommended in various combinations. If the cancer is stage IV, meaning
that it has spread to
distant organs, chemotherapy can be utilized to slow the progression of the
disease. Also, radiotherapy can be used
to control pain or symptoms of the disease at various sites.
Research
& Clinical Trials
A
person diagnosed with lung cancer should consider participating in a clinical
trial. Protocols often evaluate new
agents or combinations of agents that may have beneficial effects in the
treatment of lung cancer patients. In addition, there are ongoing protocols at
Emory University in which radiation and different chemotherapy agents are given
in a variety of ways to maximize the beneficial effects in lung cancer. Click here for more information regarding
protocols for lung carcinoma at Emory University.