Different Types Of Radiation Therapy (External Beam Radiation Therapy, Brachy Therapy) are used to kill cancer cells where very high energy radiation, called ionizing radiations are used (in MeV range).
Radiotherapy is a very essential treatment modality for cancer management. It is used as alone or combined with surgery or chemotherapy, more than 40% of cancer patients require radiotherapy. In conventional radiation therapy, side effects are more but in the modern scenario, the side effects are very low. The modern treatment modalities are VMAT, IMRT, IGRT, SRS, SRT, etc.
Radiation therapy side effects vary from patient to patient, few patients face very high-grade side effects and few patients face very low-grade side effects. Side effects of radiation therapy can be managed and treatable.
What is Radiation Therapy(Radiotherapy)?
A high energy ionizing radiation like X-Ray ( MV range ), Gamma-ray, electrons, protons, etc are allowed to pass-through cancer cells very accurately and precisely & as a result directly or indirectly radiation damages the DNA of cells.
DNA is the genetic material that controls the growth of Cells. For normal cells, DNA controls the growth rate, and the cell division process becomes natural. But for cancer cells, there is no control of DNA on the repopulation rate that’s why no of cancer cells increases rapidly
To stop this uncontrolled growth of cancer cells, we have to remove the cancer cells from the body (done by surgery) or have to kill them inside the body. Using radiation & chemo, cancer cells can be killed inside the body.
In the case of radiotherapy, cancer cells can be killed by damaging DNA. Here the DNA damage means DNA strand break, After DNA damage, the cell may repair or dye. In a certain dose per fraction, the repair mechanism of normal cells is better than cancer cells ( what we want ). The radiation is delivered in such a way that cancer cells will dye & normal cells will repair.
Normal cells require a minimum of 6 hrs to repair, so between two fractions of radiotherapy minimum 6 hrs gap should be there. When the tumor is exposed to radiation, both cancer cells, and normal cells, normal critical organs are exposed. Due to the normal structure irradiation, the side effect term arises.
Radiation is not effective for all types of cancer because of their radio-sensitivity. Radio-sensitivity of a cell means how much it sensitive to radiation. It is difficult to kill low sensitive cancer cells by radiation.
Radiation is delivered before surgery to shrink the tumor, called neoadjuvant therapy, and delivered after surgery to destroy the remaining cancer cells, called adjuvant therapy. It is also delivered with Chemotherapy to increase the radiosensitivity of cancer cells, called concurrent therapy ( CT+RT), and also the outcome is better.
Types of Radiation Therapy
- External Beam Radiation Therapy(EBRT)
- Brachy Therapy
External Beam Radiation Therapy(EBRT)
In EBRT, a beam of radiation directs externally at a tumor i.e. radiation dose is delivered to a specific part body. Suppose a patient has rectal cancer, in this case only pelvic part is irradiated.
A big volume tumor can be treated with EBRT but with brachytherapy, it not possible. A deep-seated tumor can be treated with very high energy X-Ray, superficial tumor-like skin cancer can be treated with an electron beam.
There is always side effects of Radiation because it damages the DNA. But due to modern technology, radiotherapy is becoming more accurate. Modern treatment modalities like IGRT, SRS, SRT, VMAT, etc are very precise and side effects are also very low.
- CT SCAN, PET-CT, MRI. (as per requirement )
- TREATMENT VERIFICATION
EBRT radical treatment is a long term process, it takes 2-5 weeks and conventionally five fractions deliver per week. The patient can receive treatment as an outpatient basis and in between patients may face side effects ( early side effects ), but side effects will disappear within a few weeks or few months after completion of EBRT. For palliative care, a very high dose is delivered in a single fraction, it will relieve pain.
In case of late side effects ( late effects), if some patient organ received radiation dose beyond the tolerance limit, there is a chance to face difficulty for that organ. we can avoid late effects by perfect treatment planning, patient set up, perfect treatment delivery, etc.
Brachytherapy is a term used to describe the short distance treatment of cancer. A radioactive source ( like Ir-192, Co-60) is placed very near or inside the tumor and allows to deliver the dose according to perfect planning and removed.
For this treatment, the tumor must be well located and small and become impractical for a tumor of volume greater than 5 cm since it gives a very localized dose.
The dose is delivered continuously and it may be either over a short time ( temporary implant ) or over a lifetime of the source to a complete decay( permanent implant).
Types of brachytherapy
The source is placed into body cavities close to the tumor, like Ca Cervix treatment with brachytherapy. Special applicators are placed in the cervix and using those applicators source is placed as per planning and after completion of the treatment, applicators are removed. The patient can receive treatment as an outpatient basis.
The source is placed within the tumor volume. In the modern scenario, interstitial catheters are placed inside the tumor, and using that catheter source is placed as per planning and after completion of the treatment, catheters are removed.
The source is placed over tumor surface (for skin cancer, superficial cancer).
The source is placed in a lumen. ( Brachy of Oesophagus )
A single source is placed in small or large arteries.
Sources are placed into the target tissue during surgery.
The physical advantage of brachytherapy compared with EBRT is improved localized dose delivery to the target volume. The disadvantage of brachytherapy is only to treat well localized and small tumors.
Radiation Therapy Side Effects
Since in radiotherapy, healthy cells get irradiated, so side effects will be there. Two types of fo side effects
- Early Side effects
- Late Side effects
Early Side effects:
Radical RT treatment takes 2-5 weeks to complete and during this time patient will experience side effects like Skin reaction ( skin color changes ), fatigue, hair loss, nausea, vomiting, taste change, headache, etc. It will disappear after completion of treatment within a few weeks to a few months. Early effects depend on dose per fraction, total dose, overall health, area of treatment.
Late Side Effects:
Late side effects may arise after completion of treatment within a few months or years, it depends on organs. It depends on the overall dose and dose per fraction. Some of the late effects are
Spinal cord paralysis, myelitis, necrosis.
Lung-pneumonitis, persistent cough.
Eye-cataract and blindness.
How does Radiation Therapy Work?
- In Radiotherapy, Ionizing Radiation uses for Cancer treatment ( X-Ray, Gamma Ray ).
- When an ionizing radiation beam incident on the patient’s body (tumor area), it will pass through the body and produces high energy electrons.
- These electrons again interact with body water and produce free radicals.
- The free radicals are highly reactive, interacts with DNA molecules & break the DNA strand.
- The DNA breaks either double-strand or single-strand break.
- Cells lose their ability of cell division.
- Cell dye.
Is Radiation therapy painful?
In the human body, there is no such organ to detect the presence of ionizing radiation. So, Radiation therapy is not painful.