What is lung cancer?*
Lung cancer is the abnormal growth of cells in the lung, resulting in a lung tumor. If the abnormal cells originated as lung cancer cells, the resulting collection of cells is called a primary lung tumor. If the abnormal cells originated in another part of the body – such as the colon or liver – and were carried to the lungs by the blood or other bodily fluids, then the collection of cells is considered a metastatic lung tumor.
Lung cancer is the leading cause of cancer death in both men and women in the U.S. About 13 percent of primary lung tumors are considered small cell, including oat cell cancer, mixed small cell/large cell carcinoma and combined small cell carcinoma. The remaining 87 percent of lung tumors are classified as non-small cell, which includes squamous cell carcinoma, large cell carcinoma and adenocarcinoma.
How is lung cancer detected?
Lung cancer typically develops without early symptoms, so when symptoms do occur, the cancer is often advanced. A patient may see his or her physician for a persistent cough, coughing up blood, painful breathing or coughing, shortness of breath or other symptoms. Unfortunately, most primary lung cancers are diagnosed at late stages since symptoms do not usually appear in the early stages.
Primary or metastatic lung cancer can be diagnosed a number of different ways. Often, the cancer is detected during a standard chest X-ray. CT scans, PET-CT scans and MRIs also can be used to further identify a lung tumor. A lung cancer diagnosis can be confirmed by either performing a biopsy, in which a small piece of tissue is examined, or by analyzing fluid to determine whether it contains a protein specific to tumor cells. The physician then determines the “stage,” or extent, of the disease by establishing the size of the tumor and how much the cancer has spread.
How is lung cancer treated?
Lung cancer treatment depends on the type and stage of cancer. Lung cancer can be treated with surgery, radiation and chemotherapy, and these are often combined to offer the most effective treatment. Options for treating a metastatic tumor depend on the stage of the primary cancer. The various lung cancer treatments are described in detail below.
- Surgery
Surgery, or surgical resection, is often used to remove a tumor. For early-stage lung cancer, the preferred treatment for otherwise healthy patients is a lobectomy, in which the surgeon removes the affected lobe of the lung. Lobectomies can be performed in two ways. One method is called a thoracotomy, in which the ribs are cut and spread to allow the surgeon to access the lobe of lung that needs to be removed. The second type of lobectomy is less invasive and is performed using video-assisted thorocoscopic surgery (VATS). During this procedure, small incisions are made so a camera can be placed in the chest to guide the actions of the surgeon. Some patients with early-stage lung cancer may not require that an entire lobe be removed. They undergo a procedure called a wedge resection, or segmentectomy, which can reduce the amount of normal lung tissue removed.
To be effective as possible, lung cancer surgery must not only remove the visible tumor, but also eliminate any microscopic traces of the disease that remain in the surrounding tissue. Studies comparing lobectomies to wedge resections have shown that the lobectomy results in better survival rates and is more effective in removing all of a patient’s disease.
For patients whose primary lung cancer is more advanced, as well as those who have large tumors or multiple metastatic tumors that cannot be removed by lobectomy or segmentectomy, more extensive surgery is required. In these cases, surgeons may perform a pneumonectomy, during which the entire lung is removed.
Although surgery is effective for some stages of lung cancer, patients can experience significant risk of complications, including infection, bleeding, and respiratory and cardiac problems. These complications can also lead to loss of lung function and/or a decreased quality of life. Open lobectomy and video-assisted thorascopic surgery have local control rates and 5-year survival rates of 60-80 percent.
Lung cancer surgery is typically used alone for patients with very small tumors and early-stage lung cancer. However, some patients may not be well enough to undergo surgery because they suffer from other cardiac or breathing problems. For later stages of lung cancer – typically stage II and higher – surgery is often combined with chemotherapy and, perhaps, radiation therapy.
- Radiation therapy
Radiation therapy, also referred to as radiotherapy, is a non-invasive procedure that uses radiation to kill lung cancer cells. Five-year survival rates for early-stage primary lung cancer patients undergoing this type of treatment have been reported in the range of 10-30 percent, which is lower than the survival rates of patients treated with surgery.
Conventional radiation therapy, called external beam radiation therapy, typically involves delivery of wide beams of radiation that encompass both the tumor and a significant amount of surrounding healthy tissue. Wide beams of radiation are necessary because tumors move as patients breathe. During this treatment, the radiation dose is limited to decrease the toxicity to the patient that can result from injuring healthy lung tissue. Therefore, conventional external beam radiation therapy is usually delivered in small doses during 30 to 40 sessions over four to six weeks. Toxicity rates range widely in published studies, with short-term severe toxicity ranging from 10 to 30 percent and long-term severe toxicity (radiation pneumonitis) reported as 18 percent; attempts to increase the dose of radiation being delivered using conventional radiation therapy methods have resulted in even greater toxicity.
Because tumors change position within the chest as a patient breathes, it is necessary to irradiate with wide fields that include a large amount of normal surrounding tissue. However, several techniques – such as respiratory gating, breath holding and the use of frames – have been developed to better compensate for tumor motion and allow for smaller radiation fields to be used.
- Respiratory gating
Respiratory gating is a technique in which radiation is delivered when the tumor is thought to be in a certain location during a patient’s breathing cycle. Gating makes a number of assumptions about the location of the lung tumor, such as: it is always in that same location during a specific point in a patient’s breathing pattern; a patient’s breathing pattern does not change throughout a treatment; and a patient is breathing the same during a treatment as he or she was breathing during the planning phase. In reality, many patients breathe differently throughout the treatment, particularly if they are nervous or fall asleep. These changes in breathing patterns may result in errors in radiation delivery.
- Breath holding
Breath holding involves a patient’s taking a full breath and then holding it for several seconds. As the patient holds his or her breath, the radiation beam is switched on and then turned off just before the patient begins to breathe normally again. Breath holding assumes a tumor will be in a certain location when the patient inhales. This may not always be the case, depending on the depth of a patient’s breath. Breath holding also may be very difficult for patients with advanced lung disease.
- Frames
Frames enable physicians to apply pressure to a patient’s abdomen to decrease the movement of the diaphragm and the chest cavity. Although frames reduce tumor movement within the chest, they do not completely eliminate it. This technique also can be uncomfortable and may be very restrictive for patients who have baseline breathing problems or advanced lung disease.
Techniques such as gating, breath holding and frames have allowed physicians to deliver much higher doses of radiation in as few as three to five sessions with a procedure called stereotactic body radiation therapy (SBRT). This alternative treatment for lung cancer has been shown to be more effective than conventional radiation therapy, with three-year survival rates ranging from 52 to 88 percent and a five-year local control rate of 95 percent. Although SBRT enables doctors to spare more normal lung tissue than conventional methods, it still typically requires large margins around tumors to ensure that the radiation is delivered to the tumor and to account for the inaccuracies of gating, breath holding or frame usage.
- Chemotherapy
Chemotherapy is used when cancer cells are thought to be located throughout the body or they are present in a patient’s blood or other fluids (often the case with metastatic lung tumors and advanced-stage lung cancer). Chemotherapy medication is delivered orally or through an IV (into a vein), and is given to a patient either as the sole treatment or in combination with surgery or radiation. Chemotherapy affects both normal tissue and the cancer cells, so patients may experience side effects, such as severe nausea and vomiting, infections, fatigue and weight loss. Based on randomized clinical trials, chemotherapy is recommended in addition to local treatment for patients with later-stage disease. Disease-free five-year survival rates for patients treated with chemotherapy following surgery range from 48 to 89 percent, depending on how advanced the disease is.
- Radiosurgery
Radiosurgery, such as treatment using the CyberKnife® Robotic Radiosurgery System, offers patients a different option for the treatment of lung cancer. The CyberKnife System is used to treat lung cancer patients who cannot tolerate surgery, have an inoperable tumor or are seeking an alternative to surgery. Unlike traditional radiation therapy, the CyberKnife System is able to precisely identify the tumor location as the patient breathes normally during treatment, and can be used, in some cases, to treat lung tumors non-invasively. Learn more about CyberKnife for lung cancer treatment.
*Source material drawn from www.cyberknife.com. Please refer to that website for a complete listing of references used in the original information sections.
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