Читать книгу Cancer is a Word, Not a Sentence - Miriam Stoppard - Страница 19

Radiotherapy is treatment in which an area of the body is given a high dose of radiation—rays that are similar in some respects to x-rays but different in that they are produced with the intention of damaging any growing cells in the area exposed to them.

These rays are usually created in specific machines called linear accelerators and are very closely controlled and monitored by highly specialised systems.

It is important to realise that radiation, like surgery, is a local treatment. In other words, it treats the area that gets the radiation only, and has little or no effect on any cancer cells outside the area being treated. Although many people know this, it can still be confusing, and some patients are really perplexed when it is recommended that they have radiotherapy after their chemotherapy, for example after a lumpectomy for breast cancer.

The single most important feature of radiotherapy is that the radiation passes through normal structures—such as the skin or lungs or bowel or spinal cord, depending on the area of the body involved.

Nowadays it is possible to ‘focus’ the radiation very precisely in the cancer area, and to reduce the damage to normal structures in front of or behind that area. There are several ways to do this:

By using several different directions (or fields), each of which is concentrated on the cancer, but each of which affects different areas (say, of the skin or bowel).

By using radiation that has the appropriate properties for a particular cancer—for example, radiation that gives out much of its energy near the skin surface and doesn’t penetrate very far is good for superficial cancers, whereas radiation that gives most of its energy deep in the tissues does less damage to the skin.

And finally, by using tailor-made radiation fields that are ‘trimmed’ to include all of the tumour mass and very little of the surrounding normal tissues.

Obviously, the planning of radiation treatment is a major and important procedure. Nowadays, the actual imaging of the cancer area can be done with greater and greater accuracy. Although it’s a tricky and somewhat exacting process—and probably quite boring for you!—it’s crucially important because it drastically affects how much damage can be done to the cancer cells while avoiding the normal cells in the area.