Radiotherapy Feels Like a CT Scan. Is It Really Working?

Dr Vidhi Vaghasiya | MD Radiation Oncologist | Bhavnagar

“Doctor, I lie on the treatment table, the machine moves around me, and I don’t feel anything. No heat, no shock, no pain. It feels just like a CT scan. Is the radiotherapy actually doing anything?”

Yes. It is working exactly as planned even when you feel absolutely nothing.

We are used to thinking that treatment should feel like something. So when radiotherapy is painless during delivery, it is so smooth that it can almost feel too simple to be Real.

And that is the Expertise. A good dancer makes the most difficult dance look absolutely effortless.

But radiotherapy is not meant to be felt. The important work is happening invisibly.

What feels uneventful to you is actually the final step of careful imaging, planning, calculation, verification and precise delivery performed at every point!

Let me take you behind the scenes.

Before Your First Treatment

Your radiotherapy does not begin when the machine switches on for the first time.

It begins earlier, with planning. When you are at Home, Resting and wondering How much more time this thing should take?

That is when the real Deal is being Finalized. Your Treatment Plan!

First, we perform a planning CT scan. You are positioned in a carefully reproducible way, using positioning devices when needed.

Your radiation oncologist then identifies the tumour or the area at risk and also marks nearby normal organs that we want to protect.

The treatment-planning system calculates how radiation can reach the required target while reducing unnecessary dose to surrounding healthy tissues.

So although your treatment may look simple from your side of the machine, a detailed personalised plan has already been created before you enter the treatment room.

What Happens When I Lie on the Machine?

Each day, the radiotherapy team positions you according to your treatment plan.

Those small marks on your skin, your mask, or the position of your arms and legs are not random. They help us reproduce your treatment position accurately.

Modern radiotherapy machines can also take images while you are on the treatment couch.

These images let the team compare your position with the planned position and make small corrections if needed.

This is called image guidance.

There is a planned target, a planned dose, planned beam directions and a system for checking that you are positioned appropriately before treatment.

Then the treatment begins.

Why Can’t I Feel the Radiation?

Radiotherapy commonly uses high-energy photons, similar in physical nature to X-rays but delivered at therapeutic energies and doses. 

You cannot normally feel these beams travelling through your body.

You should not feel burning, electricity or heat from the beam.

That is why treatment may feel surprisingly similar to having a scan.

The machine may rotate and make mechanical sounds.

But the radiation itself is invisible and normally painless. 

Not feeling it does not mean it was not delivered.

So What Is Radiation Actually Doing?

This is where the real treatment happens.

Radiation deposits energy inside cells in the treatment area. One of its most important effects is damage to DNA, the genetic material cells need to survive and reproduce.

When enough damage accumulates, cancer cells may stop dividing or eventually die. The body then gradually clears those damaged cells. 

This does not necessarily happen the second the radiation beam touches the tumour.

Radiotherapy is therefore different from surgery.

During surgery, a tumour may physically be removed in a few hours.

During radiotherapy, the biological effect develops over time. Cancer cells may continue dying for days or weeks after radiation has been delivered. 

That is why you should not expect an immediate visible response.

Why Do I Need Several Sessions?

Many radiotherapy treatments are divided into sessions called fractions.

The schedule depends on the cancer, treatment goal and prescribed dose.

Each fraction contributes to the planned biological effect.

Between treatments, normal tissues generally have a better ability to repair radiation injury than many cancer cells. Fractionation allows us to repeatedly damage tumour cells while giving normal tissues time for recovery.

So one quiet treatment session is actually one carefully calculated part of a larger treatment course.

How Do You Know the Correct Dose Was Delivered?

Radiotherapy is supported by extensive quality assurance.

Medical physicists perform measurements and checks to make sure the equipment is operating correctly and that treatment can be delivered accurately. 

Your treatment is based on a prescription specifying the radiation dose, number of fractions and treatment area.

Behind those few minutes are your clinical team, treatment-planning systems, imaging and multiple safety checks.

Much of radiotherapy is deliberately invisible to the patient.

Do Side Effects Prove It Is Working?

No.

Please do not judge whether radiotherapy is working by how many side effects you develop.

Some patients develop skin reactions, tiredness, swallowing difficulty, bowel symptoms, urinary symptoms, mouth soreness or other effects depending on which body area is treated.

Other patients have surprisingly few problems.

Neither situation, by itself, tells us whether the cancer received its prescribed dose.

Side effects mainly reflect which normal tissues are close to the treatment area, the dose and volume treated, other treatments such as chemotherapy, and individual sensitivity. 

You do not need severe side effects for radiotherapy to work.

Effective cancer treatment does not have to hurt.

When Will We Know Whether It Worked?

That depends on the cancer and why radiotherapy was given.

Sometimes we assess response by examining you. Sometimes symptoms improve. Sometimes blood tests or tumour markers are useful. In other situations, we wait before performing CT, MRI, PET-CT or another investigation.

Scanning too early is not always helpful because radiation can cause inflammation and temporary tissue changes.

Your oncologist will therefore decide the right method and timing for response assessment.

So if you are lying on the radiotherapy couch, thinking, “Nothing is happening,” remember this:

You are not supposed to feel the radiation.

While you are lying still, your position is being checked and a treatment planned specifically for your anatomy and cancer is being delivered.

The biological effect then continues inside the treated cells after those quiet minutes on the machine are over.

Radiotherapy can be silent, painless and invisible.

That does not make it inactive.

Sometimes the most important part of your treatment is the part you cannot feel.