“Solid” tumors that have not metastasized significantly respond well to local treatment. Such tumors can either be removed surgically or destroyed using radiation, and local procedures may also be combined with chemotherapy. This approach is particularly effective for eliminating microscopic metastases in addition to the solid tumor.
Radiotherapy involves treatment with ionizing radiation. This includes any form of electromagnetic radiation and treatment with decaying radioactive substances. Accelerated particles with sufficient energy to shift the electrical charge in the atoms of the cell (which “ionizes” the cell) are also used. All radiotherapy-based cancer treatments fall into this category.
There are two types of radiotherapy: brachytherapy (short-range therapy) and teletherapy (treatment through the skin).
- Brachytherapy involves the use of radioactive materials (isotopes) which generate radiation with an effective range ranging from a few millimeters to a few centimeters. These isotopes are generally implanted in the body or in the diseased organ, where they irradiate the tumor at close range for a specified period of time. Some radiotherapists use radioactive needles to treat prostate cancer. The treatment’s success hinges on the accuracy with which the needles are placed in the prostate (a relatively mobile body part ). A more elegant example is the use of radioactive iodine to irradiate thyroid tumors. Brachytherapy is restricted to specific sites and conditions, so it accounts for less than ten percent of all radiotherapy treatment.
- Teletherapy usually employs x-rays, although proton radiation also falls in this category. The basic principle of teletherapy involves targeting the tumor with radiation aimed through the skin and healthy tissue.
All ionizing radiation has one important characteristic in common: it is not tumor-specific. The radiation also attacks healthy tissue–some areas and types more than others–but basically equally throughout. The variability in radiation’s effects is due in part to the greater sensitivity of the rapidly dividing cancer cells. The “reparability” of cells also varies for different tissues.
The non-specific action of radiotherapy, however, is a major advantage. It doesn’t give the cancer cells an opportunity to mutate and develop resistance. The genetic material of the cell is irreversibly destroyed in all the cells which are irradiated; thus, this treatment can only be used locally and selectively. Efficacy increases with more accurate targeting, as does the patient’s ability to tolerate the treatment well. Patients benefit from precise targeting of the tumor, because fewer healthy cells are destroyed. The more accurate the targeting, the better it is for the patient.