Abstract: We included 14 RCTs analysing 1280 participants. The vast majority of participants did not receive radiotherapy to the head and neck, so this review primarily assesses prevention of chemotherapy-induced oral mucositis. All studies were at high risk of bias. The following results are for the main comparison: oral cryotherapy versus control (standard care or no treatment). Adults receiving fluorouracil-based (5FU) chemotherapy for solid cancers Oral cryotherapy probably reduces oral mucositis of any severity (RR 0.61, 95% CI 0.52 to 0.72, 5 studies, 444 analysed, moderate quality evidence). In a population where 728 per 1000 would develop oral mucositis, oral cryotherapy would reduce this to 444 (95% CI 379 to 524). The number needed to treat to benefit one additional person (NNTB), i.e. to prevent them from developing oral mucositis, is 4 people (95% CI 3 to 5). The results were similar for moderate to severe oral mucositis (RR 0.52, 95% CI 0.41 to 0.65, 5 studies, 444 analysed, moderate quality evidence). NNTB 4 (95% CI 4 to 6). Severe oral mucositis is probably reduced (RR 0.40, 95% CI 0.27 to 0.61, 5 studies, 444 analysed, moderate quality evidence). Where 300 per 1000 would develop severe oral mucositis, oral cryotherapy would reduce this to 120 (95% CI 81 to 183), NNTB 6 (95% CI 5 to 9). Adults receiving high-dose melphalan-based chemotherapy before haematopoietic stem cell transplantation (HSCT) Oral cryotherapy may reduce oral mucositis of any severity (RR 0.59, 95% CI 0.35 to 1.01, 5 studies, 270 analysed, low quality evidence). Where 824 per 1000 would develop oral mucositis, oral cryotherapy would reduce this to 486 (95% CI reduced to 289 to increased to 833). The NNTB is 3, although the uncertainty surrounding the effect estimate means that the 95% CI ranges from 2 NNTB, to 111 NNTH (number needed to treat in order to harm one additional person, i.e. for one additional person to develop oral mucositis). The results were similar for moderate to severe oral mucositis (RR 0.43, 95% CI 0.17 to 1.09, 5 studies, 270 analysed, low quality evidence). NNTB 3 (95% CI 2 NNTB to 17 NNTH). Severe oral mucositis is probably reduced (RR 0.38, 95% CI 0.20 to 0.72, 5 studies, 270 analysed, moderate quality evidence). Where 427 per 1000 would develop severe oral mucositis, oral cryotherapy would reduce this to 162 (95% CI 85 to 308), NNTB 4 (95% CI 3 to 9). Oral cryotherapy was shown to be safe, with very low rates of minor adverse effects, such as headaches, chills, numbness/taste disturbance, and tooth pain. This appears to contribute to the high rates of compliance seen in the included studies. There was limited or no evidence on the secondary outcomes of this review, or on patients undergoing other chemotherapies, radiotherapy, targeted therapy, or on comparisons of oral cryotherapy with other interventions or different oral cryotherapy regimens. Therefore no further robust conclusions can be made. There was also no evidence on the effects of oral cryotherapy in children undergoing cancer treatment. We are confident that oral cryotherapy leads to large reductions in oral mucositis of all severities in adults receiving 5FU for solid cancers. We are less confident in the ability of oral cryotherapy to reduce oral mucositis in adults receiving high-dose melphalan before HSCT. Evidence suggests that it does reduce oral mucositis in these adults, but we are less certain about the size of the reduction, which could be large or small. However, we are confident that there is an appreciable reduction in severe oral mucositis in these adults. This Cochrane review includes some very recent and currently unpublished data, and strengthens international guideline statements for adults receiving the above cancer treatments.

Plain-language summary: Authors from the Cochrane Oral Health Group carried out this review of existing studies and the evidence is current up to 17 June 2015. It includes 14 studies published from 1991 to 2015 in which 1316 participants were randomised (1280 of whom were included in the analyses) to receive oral cryotherapy versus standard care (usually saline mouthrinses) or no treatment or a different treatment or a different method of oral cryotherapy, and the number of people developing oral mucositis of different severities was compared. Nearly all the evidence was on adults receiving oral cryotherapy versus standard care or no treatment. This evidence fell into two main groups: 1) adults receiving fluorouracil-based (5FU) treatment for solid cancers; or 2) adults receiving high-dose melphalan-based cancer treatment before haematopoietic stem cell transplantation (HSCT). HSCT is given to help the body to produce all types of blood cells, which are destroyed during cancer treatment. There is evidence showing that oral cryotherapy can lead to large reductions in the numbers of adults who get oral mucositis of all severities after receiving 5FU-based treatment for solid cancers. There is less certain evidence to suggest that oral cryotherapy may reduce the numbers of adults who get oral mucositis after receiving high-dose melphalan-based cancer treatment prior to HSCT. The evidence suggests that it does reduce oral mucositis in these adults, but the size of the reduction is much less certain. However, there is more certain evidence that there is a large reduction in severe oral mucositis in these adults. Oral cryotherapy did not cause any serious side effects in any of the participants of these studies, and most people seemed able to carry it out properly and complete it. The evidence presented, on the main outcome of whether or not people developed oral mucositis of all severities, is of moderate (because the nature of the oral cryotherapy treatment meant that the studies could not be 'blinded' which is a desirable characteristic of these studies) to low quality (because in addition to the above problem, the results of the individual studies were too different to give a precise result when they were combined).