Radiotherapy Vs Chemotherapy: Let's Understand The Difference And Side Effects

Radiotherapy Vs Chemotherapy: In the recent techniques, it is possible to give a very high dose of radiation to cancer cells, with Radio Surgery.

Tavishi Dogra
Written by: Tavishi DograUpdated at: Mar 12, 2020 14:00 IST
Radiotherapy Vs Chemotherapy: Let's Understand The Difference And Side Effects

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Radiotherapy & Chemotherapy both are the forms of treatment which are been advised to the cancer patients. Let’s understand this first in a layman language where we call Chemotherapy as a form of cancer treatment where a patient is given a drug that made to kill cancer cells and since the process involves prescribed drugs, the entire body is exposed to the treatment, whereas Radiation therapy or what we call radiotherapy is targeted only at the area of the body where cancer exists. Dr Tejinder Kataria, Chairperson, Radiation Oncology, Cancer Institute, Medanta - The Medicity, shares a brief understanding of radiotherapy and chemotherapy.

Let’s Understand Radiotherapy

  • Radiotherapy is a selective destructive process in which high-intensity X-Rays are focused and targeted at cancer growing within the normal body tissues. The treatment is planned with computational algorithms and CT/MR imaging to respect the tolerances of the normal organs and tissues in close areas to cancer such that no long term side effects occur.

  • The cancer cells have low capacity and abnormal blood vessels and abnormal DNA code. Radiotherapy selectively breaks the DNA chain in the nucleus of the cell by ionizing the water molecules or directly hitting the DNA backbone of hydroxyl (OH) ions. Besides the direct breakage of the genetic code of the cancer cells radiotherapy causes the blood supply to cancer to shut down by closing the blood vessels that were created by cancer for its feeding. Such a high dose breaks down the cement and concrete (fabric and support cells) that is supporting the growth of cancer cells and maintaining its viability.


  • The treatment of Radiotherapy can be a single day when it’s called SRS – Stereotactic Radiosurgery, given over 3-5 days-Fractionated stereotactic Radiotherapy (FSRT) or over 20-40 days, conventional fractionated Radiotherapy (CFRT). In SRS and FSRT a very high dose of Radiotherapy is delivered with sub-millimetre accuracy and precision using highly advanced machines like Robotic Cyberknife.
  • Once a patient undergoes Radiation Therapy, he/she might face a little side effect some may experience skin problem like dryness, itching, blistering, or peeling. The patient may also feel fatigued in case of any serious issue doctor may change the treatment plan.


In contrast to radiotherapy, Chemotherapy is the name given to drugs that are given either by a month or intravenous route and concentrate in the dividing cells, including cancer, hair, skin, bone marrow, and reproductive organs of both males & females (testis & ovary). The effects of chemotherapy include the breakdown of the cancer cells blood supply, cell wall, nucleus and cell-division machinery.

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Chemotherapy drugs

chemo drugs

Some chemotherapy drugs are metabolized/activated in the liver and then affect cancer. Most of the chemotherapy drugs are broken into waste products and sent out of the body through the liver (bile) kidney (urine). Sometimes multiple drugs are combined to increase the effect of the cell will on cancer and reduce the side-effects on the body.

What are the recent developments?

cancer development

  • Recent developments have given targeted drugs that can hit the receptors or the pegs where the cancer cells hook to grow. The side effects of targeted therapy are lesser as compared to chemotherapy. Another class of drugs available for the last few years are Immunotherapy that works with the body’s defence mechanism to kill the cancer cells.
  • A few vaccines have also been made available to prevent cancers especially cancers that are caused by viruses. We have vaccines to prevent cancer of the cervix (mouth of the uterus) and liver cancer (hepatitis B vaccine).

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