For cancer patients undergoing radiation therapy, developing a treatment plan that takes into account not only the nature and stage of the disease but also individual factors such as age and overall health is the primary consideration. Computers and a host of highly accurate diagnostic tests are very often used in developing the treatment plan that will be followed. For example, pinpointing the exact location of the tumor is essential if the radiation therapist is to deliver the correct dosage to the right spot. New diagnostic tests, such as computerized tomographic (CT) scanning and ultrasound examination, enable the therapist to tell exactly where the tumor is located.
Computers now play a vital role in individualizing radiation therapy. Complex computer programs also have been developed that calculate precisely how much radiation should be delivered. A computer can simulate a treatment plan that will deliver the right amount of radiation to kill the cancer without endangering nearby vital organs. The computer also can allow for dosage adjustments to prevent undertreating cancer cells in the tumor margins and can take other measures to minimize the possibility of failure. These careful calculations are essential because it is the last 10 or 15 percent of the total radiation dose that guarantees the destruction of the last few surviving cancer cells, thus preventing recurrence. Data processors, video display terminals, and computer graphics all space-age devices that are commonplace in today’s radiation therapy department give the radiation therapist the accuracy needed to assure successful treatment. Experiments have shown that even a few remaining cells can, in some varieties of cancer, result in total regrowth of the cancer. Indeed, without computers radiation therapy would not be the exact science it is today.
As in all cancer therapy, designing an appropriate plan for radiation therapy is a team effort involving a number of people. In this instance the treatment team is directed by a radiologist or radiation oncologist (a radiologist who specializes in treating cancer) who usually works with an’ oncology nurse, medical physicist, technicians, and others involved in this specific type of cancer therapy. Very often radiation therapy will be combined with other forms of treatment, particularly surgery. Theoretically surgery and radiation therapy are synergistic that is, they work together to produce a more positive result than can be obtained by either treatment alone. X ray eradicates the individual cancer cells or microscopic disease, but is not as effective in treating large cancers.
In contrast, surgery is the most effective way of removing the cancer mass, but it often misses the very small or microscopic disease. Indeed, it still is not known whether surgery increases the likelihood of cancer cells’ entering the bloodstream to form new cancers in other parts of the body (metastases). If this is the case, then it would appear that the radiation therapy should precede the surgery. On the other hand, preoperative radiation may increase surgical complications such as infection, slower healing, weakened suture lines and other problems. These can be minimized by careful timing of the two procedures, planning the surgical incision lines with respect to radiation ports, and paying particular attention to the overall condition of the patient.
Chemotherapy is also combined with radiation therapy to treat many cancers. For example, radiation therapy is often combined with chemotherapy in the treatment of Hodgkin’s disease and certain breast cancers. When the two therapies are combined, special care must be taken to avoid possible adverse interactions. For example, the lungs are especially sensitive to radiation, and treatment involving the chest often results in radiation-caused lung disorders. These are usually relatively minor and heal in time. However, if the anticancer drug also affects the lungs, as is the case with bleomycin an agent used to treat cancers of the mouth, oral cavity, and testes—then particular care must be taken in combining the two therapies to avoid serious, even fatal, lung complications. Similarly, combining radiation therapy with the use of methotrexate, a drug used to treat leukemia, may result in severe nerve damage.