John: Hello, I'm John Hilton, editor of the Cochrane Editorial unit. Many potentially life-saving treatments have side effects that can have a substantial negative impact on a patient’s quality of life. Therefore, alongside Cochrane Reviews that look at the potentially beneficial effects of treatments, are those that examine ways to reduce their adverse effects. One such review, newly published in July 2017 looks at ways to protect the salivary glands during radiotherapy. Review authors, Philip Riley and Anne-Marie Glenny from Cochrane Oral Health at the University of Manchester in the UK, tell us what they found.

Philip: People receiving radiotherapy to their head or neck are very likely to experience side effects, one of which is salivary gland dysfunction. This is because the radiotherapy damages the glands, meaning that they produce less saliva. This reduction in saliva flow and changes in its composition or consistency make the patient feel like they have a dry mouth. It can cause taste disturbance, difficulty chewing and swallowing, speech problems, tooth decay and oral infections. All of these result in poorer quality of life, and unfortunately, the dysfunction is permanent.
We did our Cochrane Review to see if there are effective and safe pharmacological interventions for preventing salivary gland dysfunction, as an accompaniment to the existing review that looks at treating the condition once it has developed. And, although we have come up with some promising findings, we’ve also shown the need for a more standardised approach to research in this area.

Anne-Marie: We found 39 randomised trials that included more than 3500 people. There were 14 different comparisons. But, most of the evidence was for 3 drugs: amifostine, pilocarpine, and palifermin, and we’re not able to draw conclusions about any of the other drugs that have been tested or used.
The most promising results were for amifostine, which reduced the risk of the patient developing moderate to severe dry mouth by the end of radiotherapy and, to a lesser extent, at 3 months after radiotherapy. However, we don’t know if the effect is sustained in the long-term because there was insufficient evidence of benefit a year after radiotherapy and, overall, we assessed the evidence as being low quality, so our confidence in the results is limited and they might change with further studies. There was also some very weak evidence from one small study that amifostine might increase unstimulated saliva flow up to a year after radiotherapy. However, amifostine has its own undesirable side effects and we found low quality evidence of increased vomiting, hypotension, nausea and allergic response.
The drug pilocarpine is often used to treat salivary gland dysfunction, but there is no evidence to suggest that it’s useful in the prevention of the condition. We found no reliable evidence of benefits for either the feeling of having a dry mouth or increasing saliva flow. Likewise, there was no clear evidence of a salivary gland benefit for palifermin, which is often used to prevent oral mucositis, another side effect of cancer treatment.”

Philip:  So, in conclusion, it was very disappointing that, despite finding 39 separate studies, there is still so little evidence to support the use of any one intervention to prevent salivary gland dysfunction in people receiving radiotherapy to the head and neck. There seems to have been a scattergun approach to doing research in this area, with lots of single studies testing different interventions. We’d like to see more standardisation of what to test, what to measure and how to do so, so that future synthesis of the data from trials will provide the answers that patients and clinicians need.

John: If would like to read more about the studies that have been done, watch for future updates of this review if more research becomes available and look at the Cochrane Review of treatments for salivary gland dysfunction, you can find both easily in the Cochrane Library. Just go to Cochrane Library dot com and search 'salivary gland dysfunction'.