Efficacy of mitomycin-C on anterior urethral stricture after internal urethrotomy: A systematic review and meta-analysis

Background and Aim Mitomycin-C is a potent agent that plays an important role in tissue healing and scar formation. This study aims to investigate the efficacy of Mitomycin-C in treating anterior urethral stricture after internal urethrotomy. Methods Studies evaluating efficacy of mitomycin-c for anterior urethral stricture post urethrotomy were searched using Pubmed, Scopus, Sciencedirect, MEDLINE, and Cochrane Reviews as directory databases. The search was done in March 15th 2020. Terms being used in the searching process were “mitomycin-c” or “mitomycin”, “urethral stricture”, “urethral stenosis”, “internal urethrotomy”, “optical urethrotomy” and its synonyms. Every study with the design of retrospective or prospective clinical study being done in human subject was included. Study appraisal conducted in accordance to Oxford University Center for Evidence-Based Medicine. The conclusion of each study was summarized and the calculation of random effects from every study was conducted in meta-analysis. Random effects model is chosen because small number of studies and quite different. Results Three studies involving 311patients were included in this review, all of them reported less recurrence of in patients treated with mitomycin-c post urethrotomy (p<0.001). Risk ratio of all studies was 0.41 with 95% confidence interval (0.25-0.68). Conclusion Mitomycin-C has the potential of efficacy in treating anterior urethral stricture post internal urethrotomy. Relatively few numbers of studies may impact in the strength of this review and further studies need to be done.


Background
Urethral stricture often impairs quality of life and may result in a large economic burden 1 . There are several procedures available for treating this condition, ranging from minimally invasive procedures like internal optical urethrotomy (IOU) to invasive procedure such as urethroplasty, with or without grafting, and tissue engineering 2 . However, despite the methods available, urethral stricture often recurs. Several manipulations have been tried to prevent urethral stricture, such as indwelling catheter insertion, urethral calibration procedure, and home self-catheterization. Unfortunately, repeated instrumentation can cause scar formation. Moreover, it can also complicate subsequent reconstruction, which can lead to several complications 3,4 . On the other hand, there have been several studies evaluating the effects of antifibrotic drugs such as glucocorticoid and mitomycin-C on urethral strictures. Mitomycin-C is an agent that has the potential to inhibit mitosis, fibroblast proliferation, formation of blood vessels, and synthesis of protein and collagen. This agent plays role in tissue healing process and scar formation by reducing the release of matrix proteins by inhibiting proliferative fibroblasts 5 .
To our knowledge, there have not been any systematic reviews or meta-analyses regarding the efficacy of mitomycin-C in treating anterior urethral stricture post internal urethrotomy. Thus, the present study aims to investigate the efficacy of mitomycin-C in treating anterior urethral stricture post internal urethrotomy. We hope that by conducting this review and analysis, a definite conclusion regarding the efficacy of such treatment could be achieved.

Methods
This systematic review was conducted based on guidelines from the Oxford University Center for Evidence-Based Medicine 6 . Our present study aims to determine whether mitomycin-C provide better efficacy compared to controls (without mitomycin-C) in adult patients with anterior urethral stricture after internal urethrotomy.

Amendments from Version 2
Several changes have been made. In the methods section: inclusion and exclusion criteria has been restructured, study selection, data extraction, and risk of bias assessment have also been added. In results section: study flow diagram has been changed according to PRISMA guide, risk of bias, and result of side effects have been added. In Discussion: the first four paragraph has been deleted, risk of bias has been discussed, heterogeneity has been discussed, definition recurrence has been mentioned.
Any further responses from the reviewers can be found at the end of the article ". We also used term "human" as limiting term to exclude every study that was not conducted on human subjects.

Study selection and data extraction
A single reviewer screened the articles based on the titles, abstracts, and full text. Then, the data on author, publication year, details of studies subjects, details of studies intervention, and results are extracted.

Risk of bias sssessment
Another single reviewer assessed the risk of bias using the Cochrane Risk of Bias Tool, which include random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, and selective reporting. Every domain was judged with 3 levels (low risk, unclear risk, and high risk).

Analysis and concluding the review
We evaluated the study using appraisal worksheet for randomized clinical trial from Oxford University Center for Evidence-Based Medicine to stratify the risk of bias 6 . Using Revman 5.3 software, recurrence number from all selected studies were analyzed. Data were analyzed using forest plots with calculation of random effects. It was also done using Revman 5.3 to show relative risk/risk ratio for recurrence rate variable dan p-value. We summarized the conclusion of each study at the table along with its appraisal. We decided to use random effects model since the small amount of study and the difference between them.

Literature search
Searching process (searching strategy showed in Figure 1) by using five databases found 49 study articles. There were 13 articles eliminated after screening for duplication. The remained 36 articles were reduced to seven articles after title and abstract screening, leaving seven full text articles to be reviewed. Based on study design, we eliminated three articles, leaving four articles to be summarized in systematic review and meta-analysis. The hydrogel base was injected through a small feeding tube to reach the site of stricture. All studies applied mitomycin-C after internal urethrotomy procedure and were conducted in populations with different age means. Each of studies' quality was assessed using guide from Oxford University Center for Evidence-Based Medicine; this is explained in Table 1 and Table 2.

Outcome measures
We included the studies in which recurrence was defined by a patient having obstructive symptoms, obvious stricture at retrograde urethrography, or uroflowmetry with maximum flow rate less than 12 mL/s, and stricture was measured using   retrograde urethrogram or ultrasonography of the urethra. The outcome that measured was recurrence rate (percentage).

Risk of Bias
The summary of the risk bias assessment can be found in Figure 2. Results and heterogeneity of the studies All selected articles stated that Mitomycin-C had a significant effect on preventing or delaying urethral stricture recurrence post internal urethrotomy. All studies reported that the time-based recurrence rates in the two groups differed, where lower recurrence rates were found in the group given Mitomycin-C 2,4,7,8 . From study characteristic that is quite different and small number of studies, we choose to use random-effects model in forest plot showed in Figure 3. This forest plot suggests that there were significant differences between cases and control group. It showed from risk ratio is 0.41 with 95% confidence interval of 0.25 until 0.68, with p value <0.05. As for side effects are reported minimal and insignificant 2,8 .

Discussion
All the studies included in this review treated the two groups equally and had relatively small loss-to-follow-up rates. A common problem with all the studies included in this review is that there was no clear blinding statement. Mazdak et al. 4    number of studies, that calculation may not work well. From the studies we could notice the difference in age and methods in administering Mitomycin-C, those difference might add up the heterogeneity.
All studies support the use of mitomycin-C to prevent or delay anterior urethral stricture after internal urethrotomy, which in this review defined by a patient having obstructive symptoms, obvious stricture at retrograde urethrography, or uroflowmetry with maximum flow rate less than 12 mL/s, and every stricture in this review are all primary stricture.. This was confirmed by a less rate of recurrence rate in Mitomycin-C patients 2,4,8 ; we found that those who had Mitomycin-C administered had lower incidence of recurrence during one year and 18 months of follow up (RR = 0.32, P < 0.001). This was also confirmed by a series of cases by Farrell et al. 10 , Farrell et al. 11 , and Sourial et al. 12 Mazdak et al. 4 injected mitomycin-C into the urethral submucosa and reported that patients with mitomycin-C injection had lower rates of stricture recurrence. Opposing this study, some researchers proposed that submucosal injection could increase the complication rate and reduce the duration of the effective dose within the tissue, which yielded a scientific discussion 13 . Ayyildiz et al. 14 assessed the efficacy of Mitomycin-C for preventing urethral scar by applying the agent topically to the traumatized region in rats. They concluded that mitomycin-C applied locally reduced fibrosis significantly in a dose-independent manner.
Although all studies support the use of Mitomycin-C to prevent or delay post urethrotomy urethral stricture and the side effects reported in the studies reviewed are minimal, in Ali et al. 2

Conclusion
Mitomycin-C could be used as a potential additional treatment for anterior urethral strictures after internal urethrotomy. However, further studies are required to investigate the safety and efficacy of this method for treating anterior urethral strictures, as only a limited number of studies presently exist.

Data availability
Underlying data All data underlying the results are available as part of the article and no additional source data are required.

Muhammet İrfan Dönmez
Istanbul University, Istanbul, Turkey In this study, the authors aimed to investigate the efficacy of Mitomycin-C in adult patients with anterior urethral stricture after internal urethrotomy. Three studies involving 311 patients were included and a systematic review was conducted. However, I do have some questions and concerns outlined below about their study. According to abstract, three studies involving 311 patients were included in this review. However, flowchart indicates that four articles were included. Please clarify. 1.
The search was done in March 15th 2020. If there are other current studies from the last two years, I believe that they should be updated, as well.

2.
The review mentioned different usage and dosage of submucosal injection of mitomycin-C in four studies. Is it possible to give an opinion to the reader about which application method is more ideal? The difference and heterogeneity in age and methods in administering Mitomycin-C may cause misinterpretation of the results.

3.
We included the studies in which ...... recurrence was defined .... uroflowmetry with maximum flow rate less than 12 mL/s. What are the references that the mentioned studies use to determine this threshold value?

4.
There was no assessment of side effects in two of the studies. In addition, the lack of clear concealment and blinding statement in all four studies included in this systematic review increases the risk of bias. Further, the time to recurrence cannot be clearly evaluated due to short follow-up period. This raises doubts about the reliability of the study outcomes. As a result, the main limitation of this systematic review is that the results cannot be generalized to a wider population as it only included a few studies. Based on this, giving the message in the conclusion that Mitomycin-C has potential for efficacy in the treatment of anterior urethral stricture after internal urethrotomy may mislead the reader.

5.
There several errors of grammar and syntax that need attention. 6.

Are the rationale for, and objectives of, the Systematic Review clearly stated? Yes
Are sufficient details of the methods and analysis provided to allow replication by others? Yes

Is the statistical analysis and its interpretation appropriate? Yes
Are the conclusions drawn adequately supported by the results presented in the review? Yes

Is the statistical analysis and its interpretation appropriate? Yes
Are the conclusions drawn adequately supported by the results presented in the review? Yes