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Lung Cancer Treatment

时间:2012-06-11 10:38:47 来源:电脑知识网 作者:网络整理 浏览:

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As is true of many cancers, the treatment of lung cancer depends upon a variety of factors. The most important factors are the histopathologic (diseased tissue) type of tumor that is present and its stage.

Once a lung cancer has been staged, the physician and patient can discuss treatment options. An individual then has a better idea of the value of different forms of therapy. Other factors that are taken into account include the person's general health, medical problems that may affect treatment (such as chemotherapy), and tumor characteristics.

The characteristics of the lung tumor help to separate individuals into two groups: (1) those who are at low risk of cancer recurrence and (2) those who are at high risk of cancer recurrence. Specific prognostic—disease-forecasting—factors place patients in either of these groups. In particular, the histopathologic groupings of small cell lung carcinoma (SCLC) versus non-small cell lung carcinoma (NSCLC) may be used to better predict a patient's prognosis and response to therapy.

Surgical resection, or cutting away, of the tumor generally is indicated for disease that has not spread beyond the lung. Such resection may be conducted using a variety of techniques. Thoracotomy, the opening of the chest wall for surgical procedures, and median sternotomy, surgery performed by cutting through the breastbone, are standard methods used for lung cancer surgery. Alternative approaches include anterior limited thoractomy (ALT), thoractomy performed on the frontal chest using a small incision; anterioraxillary thoracotomy (AAT), thoracotomy performed on the frontal chest near the underarm), and posterolateral thoracotomy (PLT) thoracotomy performed on the back/side region of the trunk.

ALT, in particular, is less invasive than standard thoractomy—that is, it involves less disturbance of the body by incisions or other intrusive measures. ALT may result in less surgical blood loss, less postoperative drainage, and less postoperative pain than standard thoracotomy.

Recently, surgeons have developed other less invasive procedures for the removal of tumorous tissue. For example, video-assisted thoracoscopy (VAT), otherwise known as video-assisted thoracic surgery (VATS), uses a video camera to help visualize and operate upon the lung within the chest cavity. The surgical incisions made during VAT are much smaller than those needed for thoracotomy or sternotomy.

However, some physicians caution that VAT does not allow complete lung examination to identify and remove metastases that are not detected by preoperative chest x-ray. VAT is perhaps most appropriate for Stage 1 and Stage 2 cancers that require lobectomy (surgical removal of a lung lobule) with lymphadenectomy (removal of one or more lymph nodes) and for peripheral (outer edge) lung tumors that can be removed by wedge resection. In such cases, follow-up is required to establish a long-term prognosis.

Computed tomography (CT) scans also have been added to VAT technology to improve lung cancer surgery. Experts have found that percutaneous (through the skin) CT-guided localization wires help to identify tumorous lung nodules. In this way, wires can be used to assist VAT in cases that need sublobectomy resection (partial removal of a lung lobe).

Unfortunately, surgical procedures may cause lymphocytopenia—low number of lymphocytes (white blood cells) in the blood—which is linked with shorter survival times among patients with advanced lung cancer. Lymphocytopenia may be related to a deficiency in interleukin-2 (IL-2), a hormone that controls the activity of T lymphocytes (thymus-dependent lymphocytes). Preoperative treatment with recombinant human interleukin-2 (rhIL-2) may help to prevent the lymphocyte decrease that occurs after surgery for operable lung cancer.

If the tumor is more aggressive and/or widespread, chemotherapy and radiotherapy (radiation therapy) also may be necessary. In addition to chemotherapy and radiotherapy, other treatments are now available for the management of lung cancer.

Photodynamic therapy—(PDT) may be especially useful for the care of persons with inoperable lung cancer. Photodynamic therapy begins with the injection of a light-activated drug (e.g., photofrin/polyhaematoporphyrin, lumin). Then, during bronchoscopy (examination of the airways using a flexible scope), the lung tumor is illuminated by a laser fiber that transmits light of a specific wavelength. At that time, the laser light is used to destroy the sensitized tumor tissue. Skin photosensitivity (light sensitivity) is a side effect of PDT.

The curative potential of PDT is the most exciting aspect of this therapy in lung cancer patients whose tumors are occult (hidden, unseen) on chest x-ray. The tissue-sparing effects of PDT may be particularly important for individuals with limited lung function.

Electrosurgery—Elecctrosurgery is surgery performed using a needle, bulb, or disk electrode, Nd-YAG laser therapy (neodymium-yttrium/argon laser that concentrates high-energy electromagnetic radiation to destroy tissue), cryotherapy (destruction of tissue using extreme cold), and brachytherapy (treatment with ionizing radiation) are additional tumor debulking, or size-reducing, techniques that may be performed during bronchoscopy. Such methods are especially useful for obstructive, inner cavity (intraluminal) lung tumors.

Radiotherapy (Radiation Therapy)
Radiotherapy, otherwise known as radiation therapy, is a treatment method that uses high-energy, ionizing radiation (e.g., gamma rays) to kill cancer cells. Ionizing radiation is produced by a number of radioactive substances, such as cobalt (60Co), radium (228Ra), iodine (131I), radon (221Rn), cesium (137Cs), phosphorus (32P), gold (198Au), iridium (192Ir), and yttrium (90Y). Radiotherapy may be applied to shrink a tumor that is later removed by surgery, to relieve symptoms, or to destroy malignant cells in a tumor that cannot be removed surgically.

Because cancer cells usually multiply faster than most bodily tissues, they are especially affected by radiation, which prevents cell division and the formation of DNA (deoxyribonucleic acid; human genetic material). Yet, the bodily tissues that also divide rapidly, such as hair and skin, are particularly vulnerable to radiotherapy.

The specific side effects of radiotherapy include hair loss and skin disorders (e.g., erythema, skin redness due to blood vessel congestion; puritis, itching; desquamation, sloughing-off of outer skin layers; pain; atrophy, shrinking; increased pigmentation; edema, swelling), as well as fetal damage, increased susceptibility to infection, tachycardia (increased heart rate), changes in taste perception, anorexia (loss of appetite), malaise, nausea, and vomiting.

Radiosurgery, also called stereotactic radiosurgery or radiation surgery, is a type of external radiation therapy that may be used to treat inoperable lung cancer. In this treatment, a single large dose of radiation is administered precisely to the tumor, causing little damage to healthy tissue. In spite of its name, stereotactic radiosurgery is not a surgical procedure. The CyberKnife® System is a type of radiosurgery that is being studied in patients who have lung cancer.

Forecasting the Course of Disease: Lung Cancer Prognosis
Overall, fewer than 10% of people with primary lung cancer are alive 5 years after diagnosis. But 5-year survival rates may be as high as 35 to 40% among patients who undergo surgical resection for cancer that has not spread beyond the lung. General estimates of stage-specific median survival times—the point at which 50% of patients are still living—are as follows:

Stage 1a - more than 60 months (> 5 years)
Stage 1b - about 36 months (3 years)
Stage 2a - about 24 months (2 years)
Stage 2b - about 20 months (< 2 years)
Stage 3a - about 15 months (< 1.5 years)
Stage 3b - about 12 months (1 year)
Stage 4 - about 8 months (< 1 year)

Recent findings indicate that 5-year survival rates approach 85% among patients who are younger than 30 years of age and have surgically removable lung cancers (Mizushima et al., Cancer 85:1730-33, April 1999). Researchers believe that genetic mutations may be responsible for differences in survival rates between older and younger people with lung cancer.

Nearly half of limited-stage SCLC patients who have been treated aggressively are alive after 2 to 3 years. By contrast, untreated patients with localized disease show median survivals of approximately 3 to 4 months. Extensive-stage SCLC patients who undergo comfort care have expected median survivals of 4 to 6 weeks (note: these findings are based on a group of people and may not be true for any one individual).

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