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What is the Difference Between Chemotherapy and Radiation?

By Erin J. Hill
Updated Mar 03, 2024
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The main difference between chemotherapy and radiation is that chemo uses one or more medications in the treatment of cancer and radiation uses radio waves for the same purpose. Chemotherapy combines chemicals which kill cancer cells that are delivered intravenously to the patient. Radiation involves the use of radio waves, which also kill cancer. They both may be beneficial at treating different types of cancers, as some respond better to one treatment than the other.

Both chemotherapy and radiation kill cancer cells, often by destroying their deoxyribonucleic acid (DNA). It is also true that neither method can target cancerous cells specifically, so they also kill or damage healthy cells. This can lead to severe side effects like fatigue, compromised immune function, nausea, vomiting, weight loss or gain, and malaise. The correct course of treatment for any given patient may vary, as chemotherapy and radiation are both effective treatments and sometimes a combination of the two will be used.

Although both are used in the treatment of cancer, chemotherapy and radiation differ in the processes used to administer the treatments. Chemotherapy uses chemicals and medications which are often delivered directly into the bloodstream through an intravenous line. These substances kill cells throughout the body and can effectively treat may forms of cancer and certain other diseases. Advances in medical technology may one day allow chemotherapy to target and destroy only cancerous or mutated cells that may eventually form cancer.

Radiation also destroys cells, but instead of using tangible chemicals and medications, it uses high energy radio waves to kill dangerous cells. It also gets rid of many healthy cells. This is one cause of side effects.

Although chemotherapy and radiation are both hard on the body, many patients find radiation treatments to be far more problematic in terms of troubling side effects and symptoms. Additional medications are often given to offset the side effects of both treatments, especially if a patient is having trouble eating or drinking, as this could lead to malnutrition.

Sometimes chemotherapy and radiation are used together to combat aggressive forms of cancer. They can also be combined with other methods of treatment, such as special diets or natural treatments. The overall effectiveness of any cancer treatment will depend on many factors, including what stage the disease is in and the type of cancer. In general, health care providers use the lowest level of treatment possible to prevent potential complications and painful side effects.

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Discussion Comments
By ddljohn — On Dec 27, 2011

@turquoise-- Breast cancer patients may receive both chemotherapy and radiation. My grandmother first received chemotherapy followed by a week of radiation.

I don't know if radiation therapy side effects differ from person to person. But my aunt said that radiation therapy was much better than chemotherapy. She was a little tired but it was nothing compared to chemotherapy where she was vomiting and sleepy all the time.

By burcidi — On Dec 26, 2011

@turquoise-- I guess it is a little complicated.

But what you said in the last part is correct. Chemotherapy runs through the entire system and it will kill more healthy cells than radiation because radiation is targeted to exactly where the cancer cells are and will not effect other areas.

It does appear that radiation would be better, but the advantage of chemotherapy is that the medications which are used are very specific to that individual's disease. Doctors are able to select a combination of medications based on how far along the cancer has gotten, where it is located and so forth. That kind of detailing is not possible with radiation, it's the same general treatment for everybody.

By turquoise — On Dec 26, 2011

I don't know where I got this idea from but I had the misconception that chemotherapy is also a kind of radiation treatment. In fact, I thought that this was the reason why chemotherapy patients lose their hair. I was not aware that they're completely different methods of killing cancer cells.

Even though both try to achieve the same thing through different means, I personally find them both unimpressive. Chemotherapy sounds more dangerous than radiation because how can you possibly target an area by injecting chemicals into the blood stream?

With radiation, we could at least apply the radiation to the region where cancer is present right? Wouldn't chemotherapy lead to the death of more healthy cells than radiation?

Maybe chemotherapy would be better for something like leukemia where the entire blood stream is cancerous whereas radiation would be better for something like breast cancer. But as far as I know, most breast cancer patients receive chemotherapy and not radiation. Why is this? Is it just about the side effects?

By John57 — On Dec 25, 2011

When my mother-in-law was diagnosed with colon cancer, she went through weeks of chemotherapy treatment.

I think she experienced every possible chemotherapy side effect you could have. This was a very hard and miserable time for her.

The only positive thing she said was that when her hair grew back, it was a lot thicker than it had ever been before.

After a couple of years, her cancer returned. There was no way she was going to put herself through those chemotherapy treatments again.

Even though we wanted to be selfish and keep her around as long as possible, I can understand her thinking.

The doctor said if she didn't take any treatments she would have about 6 months to live. That is all the time we had left with her, as she passed away almost 6 months to the day of that second diagnosis.

By andee — On Dec 24, 2011

@LisaLou - I also had a friend that was diagnosed with breast cancer, but she went through radiation therapy for her breast cancer.

It must depend on the type of cancer you have and how far it has progressed. She had several weeks of pretty intense radiation treatments.

Her biggest complaint was how tired she felt after about 2 weeks. That was the only radiation side effect she really complained about. Other than that, she didn't feel nauseated or have some of the other side effects you get with chemotherapy.

Everybody handles these treatments differently. I had another friend who had both chemotherapy and radiation treatments for sinus cancer, and she never completely lost all of her hair.

She experienced most all the other adverse side effects, but never had to wear the wig she bought ahead of time.

By LisaLou — On Dec 23, 2011

I have had friends and family members that have been through both chemotherapy and radiation therapy.

It seems like those that I am familiar with, have had more chemo side effects than from the radiation.

When my friend received chemotherapy for breast cancer, she lost all of her hair. She was also very sick to her stomach, tired and just had no energy the whole time.

There were many times she wondered if the treatment was really worth it. She tried to keep a positive attitude, and so far has been able to beat it.

She can really sympathize with people who are going through this type of treatment.

By lighth0se33 — On Dec 23, 2011

I have often said that if I ever found out I had cancer, I would refuse chemotherapy and radiation treatment. I have seen how sick it makes a person, and I wouldn't want what could be my last few months alive to be spent in misery.

Also, it seems like this treatment could kill people. Since it kills all kinds of cells, couldn't it easily kill you altogether?

I know that you can survive cancer with treatment, but I have also known so many people who died in spite of it. I wouldn't want to make myself so sick that I would want to die. I think I would rather pass on naturally than go through all that medical trauma.

By StarJo — On Dec 22, 2011

My cousin is undergoing chemotherapy now to treat breast cancer. Next year, she will be receiving radiation treatment. I did not know that you could get both until she told me this.

She does not yet know how radiation will affect her, but the chemotherapy has made her very ill. She used to walk down the road every day for exercise, and she hasn't been able to do this in months.

She is so nauseated that she just stays in bed most days. She has lost her hair, so she doesn't feel like going out in public, anyway.

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