Radiation therapy is the use of high energy rays to damage cancer cells DNA & destroy their ability to divide and grow. Radiation acts best in actively dividing & well-aerated cells. Roughly 60-70% of cancers require radiation treatment at some point in time, it may be used to cure cancer, to reduce recurrence to control spread or to relieve pain & compression & alleviate other symptoms. Preparation for radiation is focused on targeting high dose radiation precisely to tumor minimizing side effects by avoiding damage to normal cells.
Modern use of technology uses 3D imaging for locating the tumor, computerized planning to avoid dose to normal tissues and precise delivery by high energy X-ray machines. These high energy X-Ray machines are known as linear accelerations (Linac) which are used for external beam radiotherapy (EBRT). It accelerates electrons to produce X-Rays which in turn are used for treatment.
Internal radiation or Brachytherapy uses a radioactive source that is put inside the body of a patient in sealed needleless seeds or wires. Brachytherapy is a common treatment for cancer of the prostate, uterus, cervix, and breast.
Radiation Therapy Process
The patient first undergoes a simulation scan; in this process, a CT scan of the patient is taken along with immobilization devices (like a mask) in the position in which the patient is to be treated. Radiation oncologist then draws the outline of areas to be treated and prescribe the dose to those areas, avoiding the normal organs. Then a plan is generated according to the prescription given to the physicist. The plan is verified by the doctor and then it is taken up for treatment delivery on the Linac machine, usually the conventional plan vary according to tumor site/location, roughly it is 5-7 weeks with 5 days a week treatment. It merely takes on an average of 10 minutes for each day treatment.
Technique of Treatment
To avoid normal organs advanced form of techniques of radiation planning are used by us – 3DRT (conformal Radiotherapy), IMRT (Intensity-modulated radiation therapy), IGRT (Image-guided radiation). SRS (Stereotactic radiosurgery) or SBRT (stereotactic body radiotherapy) are ultra-precise technique for very high dose radiation to tumor site. Deep inspiration breath-hold (DIBH) technique of Respiratory gating for lung and breast cancer treatment.
Future ahead in radiation treatment lies with shorter duration of treatment with high dose delivered in each fraction like proton therapy or high hypofractionation which would reduce the burden of stay of patients for long duration and in turn increase the compliance of treatment.