The overall goal of a meta-analysis is to combine the results of previous studies to arrive at a summary conclusion about a body of research. It is most useful in summarizing prior research when individual studies are too small to yield a valid conclusion. In this study, we analyzed the associations between obesity and surgical complications and post-operative prognosis using a meta-analysis to obtain a powerful conclusion. To the best of our knowledge, this is the first meta-analysis providing comprehensive insights into the effects of obesity status and risk associated with surgical complexity and complication score. Results of our study also indicated that obesity is a risk factor of the low surgical complex score and tend to influence the surgical complication score. We found that heterogeneity was very low among included studies, low heterogeneity proved that this conclusion had sufficient probative value. It was well known that the difficulty of surgery was related to the possible complications during surgery, and our study also drew this possible conclusion, but due to the lack of specific groups of intraoperative complications, it was difficult to assess whether there was a certain correlation according to this study. Patients were obese before surgery tended to be with more severe surgical complications, such as wound infection, intestinal complications, and 30-readmission rate. We could see that obesity affected the occurrence of complications in surgical complications, but there was no significant statistical difference between them, and we found that heterogeneity was large, which might be related to the sample situation between the studies, our funnel plot indicated that there was some publication bias in the included studies. After sensitivity analysis, we eliminated one of the most heterogeneous articles, and still saw no significant statistical difference between them (see Supplementary Fig. 1–2 for details). However, obesity did differ statistically significantly with other separately enumerated surgical complications such as deep vein thrombosis, incision infection, intestinal complications, and 30-readmission rate, and the heterogeneity was moderate. Compared with non-obese patients after ovarian cancer surgery, the obese patients were more likely to have shorter prognosis free survival. Even though most of the trials had small sample sizes and simple methodological quality, analysis of the pooled data showed a consistently superior effect of obesity combined with complications and prognosis in terms of total effectiveness, when compared to the control groups. As mentioned above, obesity was supposed to be related to more surgical complications, and obesity might be a potential risk factor for poor prognosis. The possible mechanisms were as follows: (1) Obesity and ovarian cancer: the impact of obesity itself on the occurrence, development, and prognosis of ovarian cancer, including metabolic factors and cytokine microenvironment factors [25, 26]. However, due to the existence of the “obesity paradox”, that is, some scholars believed that obesity could prolong the survival time of tumor patients to a certain extent and improve the prognosis of obese patients, but some scholars believed that it was not seen to have a significant correlation with ovarian cancer opposed to colon cancer [27]. (2) Obesity increased the occurrence of other comorbidities: obesity was accompanied by other obesity-related comorbidities, such as type 2 diabetes, hyperlipidemia, and other metabolic diseases, which affected the surgical complications and post-operative prognosis of obese patients with epithelial ovarian cancer to some extent [28]. (3) Obesity affects the operation complexity: obesity affects tissue exposure and separation during the operation process, increases the difficulty of surgery, prolongs the operation time, causes more intraoperative bleeding, affects healing, and increases the occurrence of related surgical complications, which is consistent with the results obtained by our research. However, at present, obese patients with early-stage ovarian cancer and young patients who need fertility-preserving surgery can reduce the occurrence of related surgical complications relatively through laparoscopic surgery, but it is not impossible.
Limitations
The present meta-analysis has the following limitations that must be considered. Firstly, heterogeneity was substantial among studies although we performed a subgroup analysis to explore the source of it. This may be due to the study design, sample size, age and so on. Secondly, paucity of data in some included studies prevented us from evaluating influence of FIGO stage, differentiation grade, histological subtype, presence of ascites, CA125 levels, presence of distant metastases, intraoperative situation and receiving chemotherapy or not after surgery. Thirdly, potential publication bias is very likely to exist, despite no evidence obtained from our statistical tests and language of studies was limited to English, which may result in potential language bias.