From OncoLog, November 2005, Vol. 50, No. 11
DiaLog: Radiation Therapy and Lung Cancer
by James D. Cox, M.D., Professor and Head of the Division of Radiation Oncology
While surgical removal of a malignant tumor is the preferred way to treat lung cancer, surgery isn’t always feasible. Many patients cannot have the tumor removed, either because medical conditions make the operation too risky or because the tumor has involved structures that cannot be removed. In these patients, as long as the cancer has not metastasized, radiation therapy still offers a real chance of cure.
Small tumors in the lung can be treated with radiation therapy alone. Cancer cells in tumors no larger than an inch can usually be killed; the dead cells are removed by normal physiologic mechanisms, and the amount of normal lung damaged is small. A recent study showed that three-dimensional techniques that deliver high doses of radiation in the precise shape of the tumor are more effective than older techniques. Higher radiation doses may be given to the tumor while avoiding most of the normal lung. Small tumors in certain locations can even be treated with three or four very high doses using computed tomography scans before each treatment to pinpoint the tumor. Results with such treatments have been reported to be similar to results with surgical removal.
Combining radiation therapy with chemotherapy can still cure some patients with larger tumors, especially ones that have spread to lymph nodes in the chest. Although these combined treatments have resulted in side effects in the past, newer targeting techniques such as three-dimensional conformal radiation therapy, or 3D CRT, and intensity modulated radiation therapy, or IMRT, avoid normal tissues better and result in less frequent and milder side effects. A study done at M. D. Anderson showed it was possible to give more chemotherapy in combination with 3D CRT than was possible with older techniques. M. D. Anderson investigators have also reported higher cure rates from giving chemotherapy and radiation therapy at the same time than previously reported.
Progress in the future is expected to come from combining new molecularly targeted therapies with radiation therapy and chemotherapy for inoperable tumors. We have seen striking effects with one of these agents, Iressa, on lung cancer in a small number of patients. We have seen major benefits from adding an antibody against part of the cancer cell with radiation therapy in cancer of the head and neck.
Progress is also expected from the use of proton therapy for lung cancer. Proton therapy can give very high radiation doses to the tumor while avoiding the lungs, heart, and esophagus better than the most sophisticated x-ray techniques. The Proton Therapy Center at M. D. Anderson is nearing completion. Molecular targeting and physical targeting with protons, plus chemotherapy, will be a major thrust for research and treatment of lung cancer in the years ahead.
For more information on this topic or for questions about M. D. Anderson’s treatments, programs, or services, call askMDAnderson at (877) MDA-6789.
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