Many patients who are treated with radiotherapy for head and neck cancers end up with long-term lifelong swallowing problems afterwards because the swallow muscles are very close to the tumour and can be damaged by radiation. We chose to investigate this by seeing if a form of radiotherapy where dose to the pharyngeal muscles can be reduced would improve swallowing function by reducing the degree of damage to the radiation muscles.
So we undertook a randomised controlled trial of patients with advanced head and neck cancer, mostly oropharyngeal cancers. Patients were randomly assigned either to receive standard IMRT treatment or to receive the test arm of dysphagia optimised IMRT which is called DOopt-IMRT in this trial presentation.
We randomised 112 patients in the trial. The primary endpoints were the MDADI which is a patient reported scoring system of swallowing function. We determined that patients who had the dysphagia optimised IMRT technique had a better swallow function after treatment and the MDADI difference was about 7.5 points.
In addition to that primary endpoint, which was significant with a p-value of 0.03, we looked at patient reported outcomes. We found that patients who were treated with the dysphagia optimised IMRT technique reported that nearly 40% of patients who received the dysphagia optimised IMRT recovered a swallow back to normal again after radiotherapy. That compared to only 15% of patients who were treated with the standard IMRT so an improvement in return to normal swallow of 25% which is a very large difference.
So this represents the first randomised trial that has looked at IMRT specifically to improve swallow function in head and neck patients. We think this trial is widely applicable to the majority of patients who have throat cancers who are treated with radiotherapy. We think that this will be a long-term benefit for patients and will lead to years’ equivalent of improved swallowing for patients after treatment.
Is this a simple procedure?
The technical aspects of delivering this complex form of IMRT are quite a challenge. The muscles of swallowing are not something which are routinely imaged and included in radiotherapy treatment planning. So there is a step change required for both the radiation oncologists who have to learn the anatomical position of these muscles, how to identify where they are on a CT scan and use those as an avoidance structure for radiotherapy. The medical physicists also will need to take longer to identify the radiation dose to these muscles and try really quite hard to reduce the dose to those areas because they’re very close to the tumour.
One of the things we did look at in the study and in any radiation trial where you’re reducing the volume of area receiving high dose there is always a concern that one might end up under-dosing parts of the tumour and that might lead to tumour recurrences. We didn’t demonstrate that in the trial, the numbers of patients who did recur was very low altogether and between the two arms of the randomisation within the trial they were very comparable. So it’s more work for the clinician, it’s more work for the radiation physicists but we think this translates to years, maybe decades, of improved swallow for each patient treated.