Local therapies (operation and radiation)
Solid tumour growth is a domain for local treatment, where the dissemination of the tumour is restricted. Tumours of this type can either be removed surgically or destroyed through means of radiation, and such local procedures may be combined with chemotherapy. This approach is particularly effective if the intention is also to treat microscopic metastases in addition to the solid tumour.
Treatment using ionizing radiation
Radiotherapy involves treatment using ionizing radiation. This involves the use of any form of electromagnetic radiation and radiation resulting from radioactive decay. Moreover, radiotherapy relates to the use of accelerated particles if they have energy sufficient to shift the electrical charge in the atoms of the cells, meaning to "ionize" it. All the treatments which use radiotherapy to combat cancer are included within this category. The effect in each case is the same: Ionization causes the formation of chemical radicals in the cellular fluid; such radicals damage the genetic material and thus lead to cell death.
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 over a range measured in millimetres to centimetres. These isotopes are generally implanted in the body or in the diseased organ, where they irradiate the tumour at close range for a specified period of time. Some radiotherapists use isotopic needles for the treatment of, for example, prostate cancer. The success of such a treatment hinges on the accuracy with which the needles are placed in the prostate (a gland which is relatively movable). A more elegant example of this treatment is the use of radioactive iodine to irradiate thyroid tumours. Brachytherapy is always restricted to specific sites or conditions, and therefore it accounts for only a single-digit percentage of all radiotherapy.
- Teletherapy is generally understood as a process using x-rays, although proton radiation falls under this definition as well. The basic principle of teletherapy involves the targeting of radiation at the tumour, directing it through the skin and healthy tissue.
One key property is common to all ionizing radiation: It is not tumour-specific. The radiation also attacks healthy tissue--with substantial quantitative fluctuations--but basically it does so in equal measure. One of the factors governing the variation in effects relates to the higher sensitivity of the rapidly dividing cancer cells. Additionally, the "reparability" of cells varies for different tissues.
The non-specific action of radiotherapy, however, constitutes the advantage of the treatment. 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, and consequently, therapy of this nature can only be used locally and selectively. The efficacy of the treatment increases with the accuracy of targeting. Tolerance to radiation therapy is also dependent on accuracy. Patients benefit from precise targeting of the tumour, because healthy cells are then spared destruction. The more accurate the targeting, the better it is for the patient.