Chemotherapy (chemo) and radiation are both cancer treatments, but they work in very different ways and are used for different reasons.

Super quick breakdown

  • Chemo = cancer-fighting drugs that travel through your whole body (systemic treatment).
  • Radiation = high‑energy beams (like X‑rays) aimed at one part of the body (local treatment).

Both aim to kill or shrink cancer cells, prevent them from spreading, or ease symptoms like pain.

How they work

Chemotherapy

  • Uses strong medicines (cytotoxic drugs) that go into the bloodstream and circulate through the body.
  • These drugs target fast‑growing cells, which include cancer cells but also some healthy cells (like hair, blood, and gut cells).
  • Can treat cancer that has spread (metastasized) because it reaches almost everywhere in the body.

Radiation therapy

  • Uses high‑energy beams (X‑rays, protons, or other radiation) focused on a specific area of the body.
  • Damages the DNA inside cancer cells so they stop dividing and eventually die.
  • Mostly treats one region (for example, a brain tumor, a breast, part of the prostate), so it’s called a local treatment.

Key differences at a glance

Below is an HTML table since you asked for structured info.

html

<table>
  <thead>
    <tr>
      <th>Feature</th>
      <th>Chemotherapy</th>
      <th>Radiation therapy</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>What it uses</td>
      <td>Anti‑cancer drugs (cytotoxic medicines).[web:1][web:5][web:7][web:9]</td>
      <td>High‑energy beams (X‑rays, protons, etc.).[web:1][web:3][web:5][web:9]</td>
    </tr>
    <tr>
      <td>Where it works</td>
      <td>Whole body (systemic treatment).[web:1][web:5][web:7][web:9]</td>
      <td>Mainly one area (local treatment).[web:1][web:3][web:5][web:7][web:9]</td>
    </tr>
    <tr>
      <td>How it’s given</td>
      <td>IV drip, injection, or pills by mouth.[web:1][web:5][web:7]</td>
      <td>Machine aiming beams from outside the body, or radioactive material placed inside/near the tumor (brachytherapy).[web:3][web:5][web:9]</td>
    </tr>
    <tr>
      <td>Main goal</td>
      <td>Kill or shrink cancer cells throughout the body, stop spread.[web:1][web:5][web:7][web:9]</td>
      <td>Kill or shrink cancer cells in one specific area, relieve local symptoms.[web:1][web:3][web:5][web:9]</td>
    </tr>
    <tr>
      <td>Typical side effects</td>
      <td>More whole‑body: fatigue, nausea, hair loss, low blood counts, infection risk.[web:1][web:5][web:7]</td>
      <td>More local: skin irritation or burns in treated area, local pain or soreness, fatigue.[web:1][web:3][web:5][web:9]</td>
    </tr>
    <tr>
      <td>When it’s often used</td>
      <td>Cancers that have spread, blood cancers, or as extra treatment before/after surgery or radiation.[web:1][web:5][web:7][web:9]</td>
      <td>Solid tumors in a defined area, sometimes instead of surgery or after surgery to “clean up” remaining cells.[web:1][web:3][web:5][web:9]</td>
    </tr>
    <tr>
      <td>Treatment schedule</td>
      <td>Given in cycles (treatment days followed by rest days or weeks).[web:1][web:5][web:7]</td>
      <td>Usually small daily doses over several weeks (Monday–Friday) or a set number of focused sessions.[web:3][web:5][web:9]</td>
    </tr>
  </tbody>
</table>

What they feel like (in general)

Everyone’s experience is different, but in broad strokes:

Chemo side effects

  • Commonly reported:
    • Tiredness and weakness
    • Nausea or vomiting
    • Hair loss
    • Mouth sores, changes in appetite
    • Higher infection risk from low white blood cells
  • These happen because chemo affects many fast‑growing healthy cells along with cancer cells.

Radiation side effects

  • Tend to be focused on the treated area:
    • Skin redness or peeling where the beam hits
    • Soreness or swelling in that region
    • Trouble swallowing if neck/chest is treated, or bowel/bladder issues if pelvis is treated
  • Fatigue is also very common, especially toward the end of a course of treatment.

Online forums show a mix of experiences: some people feel chemo is harder, others say radiation hit them worse, often depending on the cancer type, dose, and their overall health.

When doctors choose one, the other, or both

Doctors look at:

  1. Type and stage of cancer
    • Chemo is often used when cancer cells are likely to be spread beyond one spot.
 * Radiation is heavily used for tumors that can be targeted clearly in one area.
  1. Goal of treatment
    • Cure or long‑term control.
    • Shrink a tumor before surgery.
    • Kill remaining cells after surgery.
    • Relieve symptoms like pain, bleeding, or pressure.
  1. Your overall health and other conditions
    • Some people can’t safely get certain chemo drugs or certain radiation doses, so plans are adjusted.

Very often, people get both chemo and radiation, either at the same time (chemoradiation) or one after the other, because they can work together to improve control of the cancer.

A simple way to picture it

  • Think of chemo like a medicine that travels through all the “roads” of the body, hunting cancer cells wherever they might be hiding.
  • Think of radiation like a very focused spotlight burning cancer cells in one neighborhood at a time.

Important note

This explanation is for general understanding and can’t replace advice from a cancer specialist. Treatment decisions are very individual and depend on the exact cancer type, stage, test results, and your health overall.

If you (or someone you care about) is facing this choice, the safest next step is to ask the oncology team:

  • Why are you recommending chemo, radiation, or both for this specific cancer?
  • What are the main goals (cure, control, symptom relief)?
  • What side effects should I expect in the first weeks vs. later?

Information gathered from public forums or data available on the internet and portrayed here.