Chemotherapy VS immunotherapy. Understanding the difference.

By Awaana Health

Nov 1, 2022

Man is mortal — well, that remains a fact that we have all grown up with. But despite that severe truth of humankind, what defines the intellectual greatness of this species is the lack of a submissive attitude. Despite knowing that the battle, when it comes to the wrath of diseases and their treatment, is far beyond our control, doctors and scientists have been devoting years of their lives to not only put up a fight against any kind of disease but also try and defeat them. Different kinds of medical therapies and techniques have evolved over the years that cater to the varying needs of patients. Two such well-known modes of treatment are immunotherapy and chemotherapy. While we all must have heard of them pretty much in our daily life, not many of us would know what distinguishes the two from each other. Therefore, it’s pertinent to get some basic idea of how different methods of treatments affect the final result and what necessitates the employment of those different techniques while also trying to grasp what edge one technique holds over the other. Thus, we start by drawing a brief idea of the definition of chemotherapy and immunotherapy.

What are chemotherapy and immunotherapy?

Chemotherapy, as the name suggests, is a treatment procedure that relies on the use of chemicals and artificial products to cure a disease. We are most likely to come across this term in cases of cancer. It forms an essential part of cancer treatment where it goes into our body and interferes with the division of the carcinogenic cells by tapping their multiplication and propagation. While sometimes the chemical is infused into the body in the form of tablets, at most times it’s intravenously injected into the bloodstream.

Immunotherapy, on the other hand, is a technique that is backed by one’s own immune system and makes use of it to treat a disease. Immunotherapy drugs are administered to strengthen or alter the performance of the immune system. Some drugs enhance the functionality of the immune system whereas others add to its functions and diversify its working. It creates a stronger immune system to identify and kill cancer cells and thus, treat a patient. While chemotherapy can target and inhibit the functioning of non-carcinogenic normal cells as well, immunotherapy acts mainly on the target cells and doesn’t interfere with the functioning of normal cells, thus having lesser side effects. CAR T-cell Therapy, cancer vaccines, and immunomodulators are different types of immunotherapy and are generally administered alongside other treatment methods.

How exactly do chemotherapy and immunotherapy work?

As stated above, chemotherapy depends largely on chemicals and drugs and can either be injected into the body or taken as pills. They contain cytotoxic agents, which are compounds that are toxic to living cells. As a result, they suppress their divisional activities by destroying the constituents of DNA and thus robbing them of their ability to reproduce new cells. Thus, the cells die off. Since cancer cells divide very rapidly, their DNA is mostly exposed and thus mostly killed by the cytotoxins without sparing them much time to repair themselves. Another component is microtubule stabilizers that ‘stabilize’ the microtubules which are minute bead-like bodies that come together to help the cells with division and then disintegrate. By ‘stabilizing’ these cells, their disintegrating activities are blocked, thus making them ineffective. These are two general examples of how chemotherapy works.

Coming to immunotherapy, it works by modifying the immune system and fighting off the cancer cells which are not perceived as dangerous by the immune system, until it is ‘told’ so. To ‘tell’ that to the immune system and prepare them against the disease-causing cells, we need to induce changes in our body, which is done through a therapy called immunotherapy. These drugs remove the checkpoints attached to the cancer cells and thus reveal them to the immune system as alien harmful cells, which it then fights. Thus, the natural defense system of our body is used to treat diseases such as cancer.


As stated above, chemotherapy comes with a fair amount of side effects. This is because the cytotoxins present in the chemicals administered to the body don’t differentiate between cancerous and non-cancerous cells. As a result, it also acts upon other cells of the body which, as a part of their normal routine, also divide rapidly. One such set of cells is the hair cells. Therefore, the cytotoxins act on those cells and inhibit their functioning as well. As a result, one encounters rapid hair fall and loss of hair. Other cells that are affected are skin cells, blood cells and skin cells. One can also suffer from nausea and vomiting as the cytotoxins interact with the ‘chemo-receptor trigger zones’ (CTZ) in the mucosa of the brain, which in turn stimulates the ‘vomiting area’.

Immunotherapy, on the other hand, doesn’t have direct side effects on the bone marrow. But as a result of breaking the inhibition checkpoints, it at times, starts to attack its own cells. Thus, the body starts encountering auto-immune side effects. Some of these side effects include skin and hair diseases, hormonal imbalances, colds, vision problems, etc. One needs to be careful and should see a doctor as these toxicities may slip into major diseases at a later point in time if left untreated.

Duration of therapy

Chemotherapy has a full course and is given in cycles, keeping in mind the requisite intervals of one or two weeks for the body to recover from the previous chemical invasion. Depending on the type of cancer and the type of drug used, an entire cycle of chemotherapy can range from 2 to 6 months. 

Talking about immunotherapy, arguments and debates have been rampant regarding its duration. While some argue to be around it for a long period, others suggest that a duration of one or two years should be good. It largely depends on the patient and also on the type of cancer that he/she has. It is generally observed that immunotherapy is not carried out beyond two years as patients start developing chronic autoimmune issues. Also, immunotherapy drugs are costly. So economically too, it is generally not very feasible to carry it beyond a certain time.

Effectiveness and success rates

Having talked about its application, side effects and even the long-term effects, it’s now time to see what are the success rates of such tedious medical processes. The success rate of chemotherapy or immunotherapy depends on the stage of diagnosis, adversity of the condition, age of the patient, etc.

As per the date of the American Cancer Society, a 100% 5-year survival rate is recorded in the case of breast cancer, the more common type of cancer, if detected in stage 1. Lung cancers have a 5-year survival rate of 19% as they are mostly detected during a later stage. The five-year survival rate for prostate cancer overall is an encouraging 99%. It’s easier to mitigate the disease using chemotherapy if there has not been a distant spread.

In immunotherapy, the average response rate is between 20-50%. In cases of non-small lung cancers, immunotherapy has been found to increase the average 5-year survival life from 5.5 to 15%. In stage 4 cancers, immunotherapy has a better success rate than chemotherapy.

Thus, we end this article with an expectation that by the time you are reading this, you have acquired significant knowledge regarding chemotherapy and immunotherapy and while exiting this page you’d be reinforced with a more sound and holistic idea of what cancer treatment methods are all about.

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