Bladder cancer is the most common malignant tumor of the urinary system.13 In 2018, about 200,000 people died of bladder cancer worldwide, accounting for 2.1% of the cancer-related deaths. The most common histological type of bladder cancer is urothelial carcinoma, accounting for about 90% of all bladder cancers.14,15 For urothelial cell muscle-invasive bladder cancer and non-urothelial cell bladder cancer, active RC is recommended. The standard treatment for RC is "total cystectomy + distal ureterectomy + pelvic lymph node dissection + urinary diversion". RC can be open, laparoscopic or robotic, each treatment technique has its own advantages and disadvantages. However, RC is a complex surgical procedure, the incidence of postoperative complications can be as high as 64%, and the 30-day postoperative mortality rate is 1–3%, and the postoperative mortality rate will increase for patients aged > 80 years.16
Diabetes is a chronic metabolic disease. Due to the absolute or relative lack of insulin, the blood sugar in the body remains at a high level for a long time. If it is not effectively controlled, it will eventually lead to cardiovascular and cerebrovascular diseases, kidney damage, retinopathy, peripheral neuropathy.17 Diabetes is one of the most serious health problems in the world today. There are 22 million people living with diabetes in the United States, and this number is expected to climb to 40 million by 2030. There are about 69.1 million diabetics in India and 69.1 million in China. The total number of people with diabetes and prediabetes has reached 140 million. There is a close relationship between diabetes and bladder cancer, and many studies have shown that diabetes can increase the incidence and mortality of bladder cancer.18
In this study, meta-analysis confirmed that diabetes can significantly increase the risk of death in bladder cancer patients after RC, resulting in poor prognosis of patients. There may be two reasons why diabetes increases the risk of death in patients after RC surgery. 1) The incidence of complications in diabetic patients is higher. Studies have demonstrated that diabetes is an independent risk factor for perioperative life-threatening complications in cystectomy patients and is positively associated with serious complications. The study by Goodenough et al. pointed out that glycated hemoglobin ≥ 6.5% and perioperative hyperglycemia were associated with an increased incidence of major complications after abdominal surgery, emphasizing that elective surgery should be more reasonably controlled for blood sugar. Mossanen et al. included 57 553 patients with RC surgery in 360 hospitals in the United States. The meta-analysis showed that the increase in complications will lead to an increase in the mortality rate of patients. 2) Diabetes can lead to tumor recurrence and progression. Type 2 diabetes is the most common type of diabetic patients, and insulin resistance and hyperinsulinemia often exist in the body. Insulin can combine with the insulin receptor on the surface of tumor cells to promote the mitosis of tumor cells.
There are few studies on the effect of diabetes on the prognosis of patients with RC after surgery, and there is no relevant Meta-analysis conducted by scholars at present, so the topic selection of this study is relatively new, and the quality of the included literature is high. However, this study also has some limitations. First, only 5 cohort studies were included, and only 2 studies reported tumor-specific mortality risk, and none of the 5 studies analyzed glycemic control after RC. Second, the sample sizes of the two studies were small, so further large-sample prospective studies are still needed for demonstration and analysis. Finally, this study only retrieved published Chinese and English literatures, and did not include dissertations, conference papers and unpublished studies. There may be publication bias caused by incomplete literature inclusion. It is proved that the stability and robustness of the results of this meta-analysis are high.
The results of this study prove that diabetes can significantly increase the risk of death after radical cystectomy in bladder cancer patients. For bladder cancer patients with diabetes, close follow-up should be performed during the perioperative period and postoperative period to monitor and control blood sugar levels to reduce the risk of related complications.