To the Editor:
We read with great interest the article by Hussain et al., “Pectoralis-II Myofascial Block and Analgesia in Breast Cancer Surgery: A Systematic Review and Meta-analysis.”1 The authors sought to evaluate the Pectoralis-II block regarding its analgesic properties for breast cancer surgery when compared with control or with paravertebral blockade. To this purpose, pain severity scores in the first 24 h and cumulative 24-h analgesic consumption were chosen as coprimary outcomes. The authors identified a total of 14 clinical trials as eligible to be included in their meta-analysis.
For the validity of any meta-analysis, the quality and integrity of the data provided in the selected clinical trials is of crucial importance. Unfortunately, due to multiple most likely clerical errors, it is extremely difficult for the critical reader to verify quality and integrity of the data that were included in this meta-analysis.
Whereas the authors report in the Results section of their article that a trial by Naja et al.2 was selected for inclusion in the meta-analysis, this article is not listed in table 1 (Characteristics of Included Studies) and is also not listed among the 14 studies that report pain severity scores in the first 24 h. Instead, a study by Versyck et al.3 appears in the table and also among the 14 studies listed to report pain severity scores but is not mentioned among the studies included.
Among the studies listed to report on cumulative 24-h opioid consumption, another study (Lykoudi et al.,4 European Society of Regional Anesthesia Abstract 2016 – coauthor Stavropoulou E is omitted in the References section) appears without being mentioned previously as being included in the meta-analysis and without being listed in table 1. On the other hand, an abstract by Kanitkar et al.,5 which is mentioned as being selected for this meta-analysis and does in fact report on cumulative opioid consumption, is not among the studies listed to report on 24-h opioid consumption.
Furthermore, a study by Syal and Chandel,6 which is mentioned as being selected for the meta-analysis, listed in table 1, and listed among the studies reporting on cumulative 24-h opioid consumption, does not actually report cumulative 24-h opioid consumption.
Besides these methodologic issues that may or may not have impacted the results of this meta-analysis, we raise another concern:
The Editor’s Perspective which accompanies this article gives the impression that this meta-analysis includes 14 randomized, controlled trials that compare Pectoralis-II blocks with paravertebral blocks and finds Pectoralis-II blocks to be noninferior. In reality, only five of the 14 trials investigate these two techniques head to head. A review of these five trials demonstrates that paravertebral blocks were performed only as single level injections in all patients who received this technique. Since previous research clearly indicates that single-level paravertebral blocks only provide unpredictable and unreliable analgesia,7,8 many practitioners perform paravertebral blocks as multiple-level injection techniques. Furthermore, if one excludes nonindexed articles and abstracts from the comparison between Pectoralis-II blocks and paravertebral blocks, the meta-analysis is reduced to 41 versus 42 patients in total for each technique, respectively.
Consequently, we feel strongly that no conclusions can be drawn regarding the noninferiority of Pectoralis-II blocks when compared with paravertebral blocks from the data presented in this meta-analysis.
Dr. Gebhard has received research grants from Hikma Pharmaceuticals (formerly Westward; Eatontown, New Jersey) Purdue (Stamford, Connecticut), and Avanos (Alpharetta, Georgia), as well as honoraria for consulting from Pacira (Parsippany, New Jersey), Milestone Scientific (Roseland, New Jersey) and Recro Pharma (Malvern, Pennsylvania), and Acacia (Indianapolis, Indiana). The other authors declare no competing interests.