domingo, 18 de abril de 2010

Modern Radiation Therapy. Changes in a Traditional Cancer Treatment Modality


Stephen Allen Christensen




Ionizing radiation kills living cells by creating breaks and cross-links in DNA. Radiation oncologists (specialists in radiation therapy) take advantage of the fact that normal cells are better able to repair damaged DNA than are malignant cells.

The goal of radiation therapy is to destroy abnormal cells without inflicting significant damage on nearby normal cells. However, due to relatively crude targeting, traditional methods of radiation therapy caused significant toxicity.

Modern technologies provide for better targeting of tumors, thereby dramatically reducing the incidence of unpleasant side effects.

Uses for radiation therapy range from definitive management of single tumors to alleviation of symptoms from metastatic disease (palliative care). Additionally, radiation therapy is valuable for shrinking certain tumors prior to surgery—thus reducing the extent of the surgical procedure—and for treating patients after surgery to reduce the risk of recurrence.

Finally, radiation may be ideal for treating patients who cannot tolerate surgery.



Stanford Cyberknife, Stanford Hospital and Clinics
Long useful for treating various cancers, radiation therapy is also notorious for causing undesirable side effects. Advances in technology are improving its reputation.

Modalities of Modern Radiation Therapy

Modalities of radiation therapy are classified into two general categories: those that are administered from outside the body (external beam therapy) and those that are administered from within the body (internal therapy).

External Beam Radiation Therapy

  • Three-dimensional conformal therapy: Detailed images generated by CT or MRI are integrated with computer-controlled radiation beams directed at the target tumor. Short, daily treatments are administered over several weeks. Mesh face masks, body molds, and freckle-like tattoos may be used to localize tumors and help immobilize the target area.
  • Four-dimensional therapy: When tumors are prone to movement (e.g., lung, liver, pancreas, breast), computer-assisted tracking of images during activation of the radiation beam augments three-dimensional conformal therapy.
  • Intensity-modulated therapy: When critical structures (i.e., nerves or vessels) are adjacent to or surrounded by the tumor, the radiation beam is subdivided into modulated “beamlets” to spare nearby normal tissues. Individual treatments usually last longer—sometimes more than 30 minutes.
  • Stereotactic radiosurgery: Useful for intracranial lesions (brain tumors, acoustic neuromas, etc.). Multiple radiation beams are directed at a single target, thus delivering a high dose of radiation to the tumor while sparing nearby structures. A rigid framework is temporarily attached to the patient’s skull to eliminate movement during treatment, which often lasts up to an hour.
  • Stereotactic body therapy: A robotic arm spins around the patient to deliver radiation to the tumor from several different angles. Markers or a rigid framework are applied to the patient beforehand to localize the tumor and limit its motion. A useful modality for spinal tumors, certain lung cancers, and for patients who cannot tolerate surgery.

Internal Radiation Therapy

  • Brachytherapy: A radiation source (radioactive seeds, pellets, catheters, balloons, etc.) is placed inside the body near the target tumor. Some forms are permanent, while others remain within the body for a short period of time. Brachytherapy is sometimes used in conjunction with surgery to reduce recurrence risk. Useful for cancers of the mouth, vagina, and cervix, and some sarcomas and prostate tumors. Patients may have to limit social contacts for up to a month, but radiation dissipates within six months or so, even with permanent implants.
  • Systemic therapy: Radioactive isotopes are administered orally or intravenously in order to target specific tumor types. Some tumors (thyroid cancer and some bone tumors) exhibit an affinity for certain isotopes (iodine-131, strontium-89, samarium-153, etc.). The tumors will absorb these radioactive isotopes while nearby normal structures are spared. Radioimmunotherapy—the use of monoclonal antibodies attached to radioisotopes—is now being used to treat non-Hodgkin lymphoma.

(Adapted from Gerber D, Chan T. Recent advances in radiation therapy. Am Fam Phys 2008;78(11):1254-62)

Recent advances in radiation therapy have expanded the utility, improved the effectiveness, and decreased the complications of this important treatment modality.


The copyright of the article Modern Radiation Therapy in General Medicine is owned by Stephen Allen Christensen. Permission to republish Modern Radiation Therapy in print or online must be granted by the author in writing.
Stanford Cyberknife



Small Cell Lung Tumor Cancer Symptoms, Treatment and Statistics


Sandra Blake; David Muñoz Carmona


Small cell lung cancer (SCLC), also known as oat cell carcinoma or small cell undifferentiated carcinoma, accounts for 10 to 15 percent of all lung cancers.

Small cell lung cancer often starts in the bronchi near the center of the chest. This form of lung cancer grows at a rapid pace and spreads quickly. Small cell lung cancer is almost always caused by smoking. According to the American Cancer Society, it is very rare for someone how has never smoked to develop small cell lung cancer.

Symptoms of Lung Cancer

People in the early stages of lung cancer usually have no symptoms. This is why lung cancer is rarely found at an early stage. Lung cancers start showing symptoms when the cancer has started to spread. Common symptoms of lung cancer are:

  • chest pain, made worse during deep breathing, coughing, or laughing
  • cough that does not go away
  • loss of appetite and weight loss
  • hoarseness
  • rust-colored spit or phlegm
  • coughing up blood
  • feeling weak or tired
  • shortness of breath
  • chronic infections such as pneumonia or bronchitis
  • wheezing

Once lung cancer has begun to spread to other organs, symptoms may include:

  • numbness or weakness in the legs or arms
  • bone pain
  • dizziness, seizures, or headaches
  • lumps near the surface of the body
  • yellow coloring of the eyes and skin

If a person is experiencing any of these symptoms, a doctor should be seen as soon as possible.

Staging of Small Cell Lung Cancer

Small cell lung cancer is classified in a two stage system. Limited stage or extensive stage is used to describe the spread of the cancer. Small cell lung cancer can also be staged from I, II, III, or IV



Limited stage is when the cancer is only in one lung and can also include lymph nodes on the same side of the chest.

Extensive stage is when the cancer has spread to both lungs, lymph nodes, and distant organs of the body.

Treatment Options for Small Cell Lung Cancer

According to the National Cancer Institute, most treatments will not cure small cell lung cancer. Surgery is rarely an option for the treatment of small cell lung cancer. Fewer than one out of 20 cases has only one tumor with no metastasis to lymph nodes or other organs.

The main course of treatment for small cell lung cancer is chemotherapy. Chemotherapy can be done alone or with radiation. Chemotherapy agents used will depend on the stage of the cancer.

Laser therapy can be done in conjunction with other therapies, such as radiation and chemotherapy. An endoscopic stent can be placed to keep an airway open if abnormal tissue growth from the cancer is causing an obstruction.

Statistics Regarding Small Cell Lung Cancer

The National Cancer Institute reports survival rates for people receiving chemotherapy and radiation treatments for small cell lung cancer are approximately 46% at two years and 26% at five years. Five-year survival rates for patients diagnosed with stage IV small cell lung cancer is only at 2%. Survival rates will vary widely for individual patients based on medical history, stage of the cancer, spread of the cancer, and response to treatments.

Clinical trials are being used for the treatment of patients with small cell lung cancer. Certain criteria must be met in order to qualify for clinical trials. Clinical trials can provide options for patients with small cell lung cancer when conventional methods of treatment are not showing improvements.

Considerations Regarding Small Cell Lung Cancer

Small cell lung cancer is an aggressive form of cancer and treatment must begin quickly. Patients should discuss in detail the treatment options available and the side effects associated with certain treatments. Treatment teams are usually available to assist patients and families with questions and concerns. Deciding what treatment plan fits best is an individual choice.

References:

1. American Cancer Society, "Small Cell Lung Cancer" accessed April 13, 2010

2. National Cancer Institute, "Small Cel Lung Cancer" accessed April 13, 201



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