A trial looking at a lower dose of chemoradiotherapy for anal cancer that hasn’t spread (PLATO ACT4)

Cancer type:

Anal cancer




Phase 2

This trial compared standard dose chemoradiotherapy Open a glossary item with a lower dose of chemoradiotherapy for anal cancer that hadn’t spread. It was for people with squamous cell carcinoma, the most common type of anal cancer.

The trial was supported by Cancer Research UK. It was open for people to join between 2017 and 2020. The team presented the results at a conference in 2023.

More about this trial

Doctors often treat anal cancer with a combination of chemotherapy and radiotherapy (chemoradiotherapy). 

The total dose of radiotherapy is split into individual doses. People usually have treatment once a day (Monday to Friday). When this trial was done, people with anal cancer often had 28 doses over 5 ½ weeks. The research team wanted to look at how well 23 doses over 4½ weeks worked.

The people in this trial had mitomycin C chemotherapy into a vein on the day they started radiotherapy. And capecitabine (Xeloda) chemotherapy tablets twice a day on each day they had radiotherapy.

Chemoradiotherapy can cause side effects. People can have side effects during or soon after treatment (short term or acute). Some people have side effects for a while after treatment (long term).

People in this trial were put into a treatment group at random. Out of every 3 people who joined the trial:

  • one person had standard dose chemoradiotherapy 
  • two people had lower dose chemoradiotherapy  

The main aims of this trial were to find out: 

  • if lower dose chemoradiotherapy is as good as the standard dose at curing anal cancer 
  • more about the side effects of lower dose chemoradiotherapy

Summary of results

The trial team found that lower dose chemoradiotherapy worked as well as standard dose chemoradiotherapy in the first 6 months after treatment.

A total of 160 people joined this trial. There were:

  • 55 people in the standard dose group
  • 105 people in the lower dose group

The research team looked at how many people’s anal cancer had gone, 6 months after treatment. 

They found it was similar in both groups:

  • 46 people (83.6%) who had standard treatment
  • 89 people (84.8%) who had lower dose treatment

Side effects
136 people taking part had at least one short term side effect from treatment. But some of these were mild or didn’t last long. Some people had more severe side effects:

  • 25 people (45.5%) who had standard dose chemoradiotherapy
  • 37 people (35.2%) who had lower dose chemoradiotherapy 

The most common of the more severe side effects were sore skin around the anus and diarrhoea.

It’s too early to know about long term side effects yet. The research team are collecting more information about these.

Quality of life
The people taking part completed quality of life questionnaires before and after treatment. The research team found that quality of life had dropped a bit for people in both groups by the time they finished treatment. But it increased back to their pre-treatment level by 6 months after treatment at the latest. 

The biggest issues were an increase in pain and tiredness, and changes in bowel function. 

Men and women in the standard treatment group found that treatment affected their sex life. This was still an issue for some people 6 months after they finished treatment.

The research team concluded that lower dose chemoradiotherapy worked as well as standard dose chemoradiotherapy. And that it caused fewer severe side effects. This was for anal cancer that hadn’t spread to another part of the body.

The people who took part in this trial are still having follow up appointments and assessments to see how they are doing. The research team want to find out more about long term side effects and how well treatment works. We hope to update this page when there are more results available.

More detailed information
There is more information about this research in the reference below. 

Please note, the information we link to here is not in plain English. It has been written for healthcare professionals and researchers.

Standard vs dose reduced chemoradiotherapy in anal cancer: short-term results of the PLATO-ACT4 RCT 
A Gilbert and others
ESTRO Conference, May 2023. Presentation number OC-0831.

Where this information comes from    
We have based this summary on the information in the article above. As far as we are aware, it has not been reviewed by independent specialists (peer reviewed Open a glossary item) or published in a medical journal yet. We have not analysed the data ourselves.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Professor David Sebag-Montefiore
Dr Mark Harrison
Professor Richard Adams

Supported by

Cancer Research UK
Stand up to Cancer
University of Leeds

Other information

This is Cancer Research UK trial number CRUK/15/007.

If you have questions about the trial please contact our cancer information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Last reviewed:

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