Abstract
Background
Cochrane Reviews are methodologically of high quality but the clinical relevance of analysed efficacy measures (EMs) should also be assessed.
Methods
The clinical relevance of EMs used in one systematic Cochrane review of oral zolmitriptan for migraine headache was evaluated.
Results
The following EMs were used: pain free at two hours (30%), headache relief at two hours (60%), sustained pain free for 24 hours (19%) and sustained headache relief for 24 hours (39%). These EMs were also used in four other Cochrane reviews of acute migraine treatment. Of these EMs sustained headache relief for 24 h is not judged clinically relevant.
Conclusion
Pain free and sustained pain free are clinically relevant, but the responses are rather low, demonstrating that there is a need for improvement of acute drug treatment in migraine.
The Cochrane Collaboration states that ‘Cochrane Reviews are systematic reviews of primary research in human health care and health policy, and are internationally recognised as the highest standard in evidence-based health care’ (http://www.cochrane.org/cochrane-reviews). With such a declaration the Cochrane Reviews should be like Caesar’s wife, that is, not even suspected of wrongdoings.
In the recent Cochrane review on zolmitriptan from 2014 it is stated (1): “In selecting the main outcome measures for this review we considered scientific rigor, availability of data, and patient preferences. Patients with acute migraine headaches have rated complete pain relief, no headache recurrence, rapid onset of pain relief, and no side effects as the four most important outcomes (2). In view of these patients’ preferences, and in line with the guidelines for controlled trials of drugs in migraine issued by the International Headache Society (IHS) (3), we considered the following main outcomes:
Pain free at two hours, without the use of rescue medication. Reduction in headache pain (‘headache relief’) at two hours (pain reduced from moderate or severe to none or mild without the use of rescue medication).
Sustained pain-free during the 24 hours post-dose (pain free within two hours, with no use of rescue medication or recurrence of pain of any intensity within 24 hours). Sustained headache relief during the 24 hours post-dose (headache relief at two hours with no use of rescue medication or a second dose of study medication, or recurrence of moderate or severe pain within 24 hours). Adverse events: participants with any adverse event during 24 hours post-dose; serious adverse events; adverse events leading to withdrawal.”
Four efficacy outcomes used in a Cochrane Review of oral zolmitriptan (Bird et al., 2014). Results for zolmitriptan (Zolmi.) 2.5 mg and placebo (Plac.) are presented.
NNT: numbers needed to treat.
The Drug Trial Subcommittee of the IHS has evaluated this problem and has published guidelines for drug trials in migraine in 1991 (5), 2000 (3) and in 2012 (6). In 1991 sustained pain free (SPF) was the suggested primary EM (5), and in 2000 and 2012 it was recommended as a secondary EM (3,6). Pain free (PF) was recommended as the primary EM in the guidelines from 2000 and 2012 (3,6). Headache relief (HR), for definition see above, is an invention of Glaxo for use in the sumatriptan trial programme (7). Despite some inherent shortcomings, see IHS Clinical Trial Subcommittee (3) for discussion, and the fact that patients want to be pain free (2), HR has been used extensively in triptan trials (8). HR has been recommended by IHS only as a secondary efficacy outcome ‘mainly to facilitate comparison of results in new randomized clinical trials (RCTs) with those of previous trial programmes for the triptans’ (3,6). In the future HR will become even less relevant because it cannot be used in trials in which patients can treat in the mild phase of headache (9). Sustained headache response (SHR) was used in triptan trials probably from the late 1990s and was advocated by Goldstein et al. in 1999 (10) as a way to address recurrences. It is, however, in my and the IHS’ view (6) not a useful efficacy outcome. There is no requirement for pain freedom, which is what the patients want (2,11), and the problem with recurrence is addressed sufficiently with the SPF outcome. In addition, patients have never expressed satisfaction with this efficacy outcome. Consequently, SHR was not mentioned at all in the IHS guidelines from 2000 (3), and in the 2012 guidelines it is stated that ‘
In conclusion: PF and SPF are clinically relevant efficacy measures and ‘the two endpoints together incorporate the main treatment attributes that determine patient satisfaction (i.e. rapid and sustained freedom from pain)’ (12), but both have relatively low absolute response rates and therapeutic gains with oral zolmitriptan 2.5 mg, see Table 1, demonstrating that there is a need for improvement of acute drug treatment in migraine. HR can be used as a secondary efficacy outcome mainly in order to allow a comparison with results in previous trials using this outcome (3,6). In contrast, SHR, lacking clinical relevance (see above), should not be used as a secondary efficacy outcome in systematic reviews. The impetus for the use of SHR is probably that SPF is very low for all triptans and SHR looks much nicer in the promotion of these drugs.
Clinical implications
Pain free (PF) and sustained pain free (SPF) should be used when judging an acute migraine trial. Sustained pain relief is not clinically relevant. PF and SPF responses are low, demonstrating the need for improvement of acute migraine therapy.
Footnotes
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Conflict of interest
None declared.