Cancer pain is an important and distressing symptom that tends to increase in frequency and intensity as the cancer advances. For people with advanced cancer, the prevalence of pain can be as high as 90%. It has been estimated that 30% to 50% of people with cancer categorise their pain as moderate to severe, with between 75% and 90% of people with cancer experiencing pain that they describe as having a major impact on their daily life. Epidemiological studies suggest that approximately 15% of people with cancer pain fail to experience acceptable pain relief with conventional management. Uncontrolled pain can lead to physical and psychological distress and can, consequently, have a drastic effect on people’s quality of life.

To determine the analgesic efficacy of hydromorphone in relieving cancer pain, as well as the incidence and severity of any adverse events.

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase and clinical trials registers up to April 2016. There were no language, document type or publication status limitations applied in the search.

We included randomised controlled trials (RCTs) that compared hydromorphone with placebo or other active pain medication for cancer pain in both adults and children. The four main outcomes selected have previously been identified as important to people with cancer; pain no worse than mild pain, and the impact of the treatment on consciousness, appetite and thirst. We did not consider physician-, nurse- or carer-reported measures of pain.

Two review authors independently extracted data. For binary outcomes, we calculated risk ratio (RR) and its 95% confidence interval (CI), on an intention-to-treat basis. For continuous data, we estimated the mean difference (MD) between groups and its 95% CI. We used a random-effects model and assessed the risk of bias for all included studies. A meta-analysis was not completed on any of the primary outcomes in this review due to the lack of data. We assessed the evidence using GRADE and created two ‘Summary of findings’ tables.

We included four studies (604 adult participants), which compared hydromorphone to oxycodone (two studies) or morphine (two studies). Overall, the included studies were at low or unclear risk of bias, rated unclear due to unknown status of blinding of outcome assessment; we rated three studies at high risk of bias for potential conflict of interest. Data for 504 participants were available for analysis. We collected data on endpoint participant-reported pain intensity measured with a visual analogue scale (VAS) (mean ± standard deviation (SD): hydromorphone 28.86 ± 17.08, n = 19; oxycodone 30.30 ± 25.33, n = 12; scale from 0 to 100 with higher score indicating worse pain), and Brief Pain Inventory (BPI) 24 hours worst pain subscale (mean ± SD: hydromorphone 3.5 ± 2.9, n = 99; morphine 4.3 ± 3.0, n = 101, scale from 0 to 10 with higher score indicating worse pain). The data demonstrated a similar effect between groups with both comparisons. The pain intensity data showed that participants in all four trials achieved no worse than mild pain. There were several adverse events: some were the expected opioid adverse effects such as nausea, constipation and vomiting; others were not typical opioid adverse effects (for example, decreased appetite, dizziness and pyrexia, as shown in Table 1 in the main review), but generally showed no difference between groups. There were three deaths in the morphine group during the trial period, considered to be due to disease progression and unrelated to the drug. Three trials had over 10% dropout, but the reason and proportion of dropout was balanced between groups. The overall quality of evidence was very low mainly due to high risk of bias, imprecision of effect estimates and publication bias. There were no data available for children or for several participant-important outcomes, including participant-reported pain relief and treatment impact on consciousness, appetite or thirst.

This review indicated little difference between hydromorphone and other opioids in terms of analgesic efficacy. Data gathered in this review showed that hydromorphone had a similar effect on participant-reported pain intensity as reported for oxycodone and morphine. Participants generally achieved no worse than mild pain after taking hydromorphone, which is comparable with the other drugs. It produced a consistent analgesic effect through the night and could be considered for use in people with cancer pain experiencing sleep disturbance. However, the overall quality of evidence was very low mainly due to risk of bias, imprecision of effect estimates and publication bias. This review only included four studies with limited sample size and a range of study designs. Data for some important outcomes, such as impact of the treatment on consciousness, appetite or thirst, were not available. Therefore, we were unable to demonstrate superiority or inferiority of hydromorphone in comparison with other analgesics for these outcomes. We recommend that further research with larger sample sizes and more comprehensive outcome data collection is required.