| Objective: Currently, the treatment of benign parotid tumors is surgical dissection, but the scope and surgical resection remains controversial. The traditional treatment of benign parotid tumors is superficial parotidectomy(SP), which includes the dissection of the branches of the facial nerve, ligation of parotid duct, removal of the whole superficial lobe of the parotid gland together with the tumor. Superficial parotidectomy is considerd to be safe and reliable. It can minimize the recurrence of the tumors. However, while the recurrence rate improves, the number of complications increases, including facial nerve paralysis, Frey’s syndrome, salivary fistula and facial malformation. Extracapsular dissection(ECD) is the minimally invasive approach of parotidectomy, which removes tumors along with a 3-mm rim of healthy tissue surrounding the resection and less or without dissection of the facial nerve. Compared with the superficial parotidectomy, extracapsular dissection is less invasive and has lower complications rate. The relapse rate doesn’t increase.Nevertheless, the controversy between SP and ECD still exists. In this study, we use systematic literature review and Meta-analysis methods to collect relatively literature about postoperative outcomes of SP and ECD, then analysis recurrence rate and complication rate by evidence-based medicine to provide a theoretical basis for the selection of the appropriate surgical approach in clinical.Methods:1 Search StrategyRelevant studies that compared the outcomes of extracapsular dissection and superficial parotidectomy for the parotid benign tumors were searched in Pubmed, CNKI and Wangfangdata databases by the end of March 2014. The following words or terms were adopted:(1) extracapsular dissection, capsule dissection,(2) parotid neoplasm, parotid tumor and parotid. These two search terms were combined using the Boolean operator ‘and’. Furthermore, we searched additional relevant studies by manual searches and reference backtracking.2 Documents ScreeningInclusion and exclusion criteria:(1) the studies could be defined as a case-control study or a cohort study,(2) the objects of studies should be patients with primary,solitary, clinically benign parotid epithelial tumors. Studies involving recurrent, multiple, malignant tumors or non-salivary original tumors were excluded,(3) Surgical techniques for ECD and SP were clearly described. In this study, ECD is defined as dissecting a thin margin of surrounding normal gland(1-to3-mm) around the tumor without planned identification of the main trunk of the facial nerve; SP is defined as removing the complete or partial superficial lobe with the tumor after planned identification and dissection of the facial nerve,(4) ECD was required for patients to be assigned the test group whereas SP was used to assign patients to the control group,(5) complete data were available with a specific number of cases(≥5),(6) at least one of the following outcomes was included(recurrence, facial weakness, Frey’s syndrome, salivary fistula). If the duration and sources of study population recruitment overlapped in two or more papers by the same authors or same centers, the most recent study or the study with the larger number of participants was included.3 Data ExtractionTwo authors independently extracted the following data for each included study, and any disagreements were resolved by consulting the third author. The factors of data extraction :(1) general information(first author, publication year, source, and author’s country),(2) study design,(3) number of cases,(4) length of follow-up,(5) incidence of recurrence, Facial weakness, Frey’s syndrome and salivary fistula,(6) conclusions. In this study,expect that Chai etc. and Uyar et al were prospective studies, the rest were retrospective studies. Any disagreements were resolved by consulting the third author.4 Statistical AnalysisMeta-analysis was performed using software Rev Man 5.0. The Odds Ratio(OR) with 95% CI was determined for dichotomous data. The significance level was set as 0.05. Heterogeneity between studies was detected with a Chi-square test before pooling data, and the quantity of heterogeneity was measured with the I2 statistic. If the I2 value was <50%, the fixed-effects meta-analysis was applied, if the I2 value was ≥50%, the random-effects meta-analysis was used. In the presence of heterogeneity, a sensitivity analyses was performed by removal of each study in turn in order to examine the stability of the main results. Potential publication bias was investigated by visual assessment using a funnel plot and further examined using a combination of the Egger regression test and the ‘trim and fill’ method with Stada 11.0.Results:1 Search results143 potentially relevant studies were obtained after initial search and reference backtracking. Then the studies were further screened according to inclusion and exclusion criteria. Finally, 15 studies were selected for the Meta-analysis, of which 4 were from UK, 3 were from China, 2 were from Greece, 2 were from Germany, one were from Norway, Turkey, US and Italy, respectively. The studies were published during the period 1979 to 2013. A total of 2,929 participants were included in those studies, of which 1,796 underwent ECD and 1,133 underwent SP. These studies included the incidence of recurrence, Facial weakness, Frey’s syndrome and salivary fistula.2 Recurrence rateFourteen studies reported the recurrence rate after surgery. The recurrence rates for ECD and SP were 1.29%(23 of 1776 cases) and 1.48%(16 of 1081 cases), respectively. As between-study heterogeneity was not observed(P = 0.76, I2 = 0.0%), a fixed effects model was used for analysis. There were no statistically significant in recurrence rate between ECD and SP(P = 0.55).3 Facial weaknessThe rates of transient facial nerve paresis for ECD and SP were 5.48%(74 of 1350) and 22.94%(139 of 606), respectively, which were reported in 10 studies..Due to significant between-study heterogeneity was observed(P = 0.01, I2 = 57%), a random effects model was used for further analysis. The rate of transient facial nerve paresis of ECD was significantly lower than that of SP(P <0.00001).The rates of permanent facial nerve paralysis for ECD and SP were 0.66%(8 of 1221) and 2.71%(15 of 554), respectively. Because between-study heterogeneity was absent in the result(P = 0.15, I2 = 41%), a fixed effects model was applied in this meta-analysis. The rate of permanent facial nerve paralysis of ECD was still significantly lower than that of SP(P =0.01).4 Frey’s syndromeThere were 11 studies that reported the incidences of Frey’s syndrome. The incidences of Frey’s syndrome in ECD group and SP group were 1.91%(26 of 1360) and 16.71%(111 of 664), respectively. Heterogeneity between studies was not detected(P =0.65, I2 =0.0%), therefore a fixed effects model was used for the analysis. It seemed that ECD could reduce the risk for Frey’s syndrome significantly(P <0.00001).5 Salivary fistulaSalivary fistula was reported by 0.53%(5 of 946) in ECD group compared to 2.96%(10 of 338) of SP patients in 5 studies. There was no significant heterogeneity among studies(P =0.34, I2 =11%). So a fixed effects model was used for analysis. There was significant reduction in salivary fistula in the ECD group compared to the SP group(P =0.03).6 Publication biasAs shown in funnel plot(with Frey’s syndrome involved in the literatures, for example), the selected literatures generally arranged symmetrically around the center. Egger regression test showed there was no publication bias among these studies(P >0.1).Conclusions:This systematic review with meta-analysis suggests that ECD has a similar recurrence rate as SP, but ECD can significant reduce the complications of facial weakness, Frey’s syndrome and salivary fistula. |
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