A trial looking at surgery for mesothelioma (MARS 2)

This trial showed that chemotherapy and surgery did not help people live longer than chemotherapy alone. Generally, those having both chemotherapy and surgery had more serious side effects of treatment. 

It cost the NHS more for people to have both surgery and chemotherapy than chemotherapy alone.

Results

392 people joined the trial and had 2 cycles of chemotherapy  followed by a CT scan. The researchers used the CT scan to look at how big the cancer was and whether it had spread.

335 people were then able to be put into 1 of 2 treatment groups. This was based on the CT scan results and how the people taking part were feeling. This part of the trial was randomised. There were:

• 166 people in the chemotherapy group
• 169 people in the surgery and chemotherapy group

Everyone had up to 2 to 4 more cycles of standard chemotherapy . And people had the type of surgery that their treatment team thought would be most beneficial.

Not everyone completed treatment on the trial. 81 out of the 335 people stopped chemotherapy after the second cycle. This was for a number of reasons including:

• their mesothelioma had got worse, or they became less well in themselves 
• they chose not to take part any longer 
• their doctor thought it was not beneficial for them to continue to take part 

12 people had died by this stage of the trial.

93 out of 166 people (56%) in the chemotherapy alone group completed 6 cycles of chemotherapy in total.

157 out of 169 people (93%) in the surgery and chemotherapy group had surgery as part of the trial. Most people having surgery had an extended pleurectomy decortication. 

66 out of 169 people (39%) in the surgery and chemotherapy group completed 6 cycles of chemotherapy in total.

The trial team followed up to people taking part for 22.4 months on average. 

They looked at how long people lived from when they joined a treatment group. They found this was on average:

• 24.8 months for people in the chemotherapy group
• 19.3 months for people in the chemotherapy and surgery group

They also looked at how many people were alive from each group after 5 years. They found it was similar in both groups. It was:

• 6 people (4%) in the chemotherapy group
• 7 people (4%) in the surgery and chemotherapy group

The researchers looked at the quality of life of people taking part. They found that this was worse for people in the surgery group.

The trial team calculated the costs to the NHS of both treatment groups. Chemotherapy and surgery together were more expensive than just chemotherapy. 

Side effects

Most people had at least one side effect that was likely to be from treatment.

There were severe side effects in both groups.

80 out of 166 people (48%) had a severe side effect in the chemotherapy group. The most common severe side effects included:

• infection 
• a breathing or chest disorder 
• digestive system problems 
• heart problems

107 out of 169 people (63%) had a severe side effect in the chemotherapy and surgery group. The most common severe side effects included:

• infection 
• a breathing or chest disorder 
• heart problems 
• digestive system problems 
• needing a second operation 

Conclusion
This trial shows that extended pleurectomy decortication with chemotherapy is not useful for this type and stage of mesothelioma. But this trial has still added to our knowledge and understanding of mesothelioma and how to treat it.

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.

Extended pleurectomy decortication and chemotherapy versus chemotherapy alone for pleural mesothelioma (MARS 2): a phase 3 randomised controlled trial
E Lim and others
The Lancet Respiratory Medicine, 2024. Volume 12, issue 6, pages 457-466.

Where this information comes from    
We have based this summary on the information in the article above. This has been reviewed by independent specialists (peer reviewed ) and published in a medical journal. We have not analysed the data ourselves. As far as we are aware, the link we list above is active and the article is free and available to view.