The research team found that using a higher dose of IMRT is safe. They think that a higher dose of IMRT also works better for people with locally advanced thyroid cancer. But they need more studies to find out for sure.

45 people took part in this phase 1 trial. Everyone had surgery to remove the cancer (thyroidectomy) and then radiotherapy with IMRT.

Of these 45 people, 15 had a low dose of radiotherapy (DL1) and 30 had a high dose (DL2).

People who join the low dose of radiotherapy group (DL1) had 28 treatments (fractions) of radiotherapy. And people who had the high dose of radiotherapy (DL2) had 30 fractions of radiotherapy.

Side effects
Doctors looked at the number of people who still had severe side effects after 12 months of treatment. They looked at the results of 12 people from the DL1 group. And the results of 24 people from the DL2 group. They found that:

• 1 person from the DL1 group had severe side effects after 12 months of treatment
• 2 people from the DL2 group had severe side effects after 12 months of treatment

A year after treatment, the researchers looked at the most common side effects in both groups. These included:

• difficulty swallowing
• narrowing of the food pipe
• difficulty breathing
• dry mouth
• swelling
• scarring of the skin
• ear problems such as hearing loss and ringing in the ear (tinnitus)
• an uncomfortable sensation in the spine, legs and arms (Lhermitte’s syndrome)

How well the treatment worked
The trial team looked at how well the treatment worked. To do this, they looked at the number of people who were alive after 5 years of treatment. This is called overall survival.

Doctors found that:

• almost 7 out of every 10 people (almost 70%) who joined the DL1 group were alive 5 years after treatment
• more than 8 out of every 10 people (more than 80%) who joined the DL2 group were alive 5 years after treatment

Conclusion
The trial team concluded that a high dose of IMRT is safe to use. But doctors still have concerns about the severe side effects people have after treatment.

Doctors also think that the high dose of IMRT works better for people with locally advanced thyroid cancer. But this trial only looked at a small group of people. Doctors need more studies to find out for sure.

We have based this summary on information from the research team. The information they sent us has been reviewed by independent specialists (peer reviewed ) and published in a medical journal. The figures we quote above were provided by the trial team who did the research. We have not analysed the data ourselves.