Effects of different status of the bladder on dosimetry to normal tissue in brachytherapy of Cervix Cancer: A Meta-analysis

Objective To assess the effects of bladder filling and emptying state on the dose distribution to normal tissue in intracavitary brachytherapy of cervical cancer. Methods We searched databases including PubMed, EMBASE, Cochrane Library, Ongoing Controlled Trial, Chinese Biomedical Literature Database, Chinese Journal FullText Database and Chinese Scientific Journals FullText Database. Quality assessment and data extract was performed for clinical research that met qualifying criteria, then we performed Meta-analysis by StatA12.0 software. Results Six studies were involved and 135 patients were included. The Meta-analysis showed that the median dose D50 to the bladder in filling state was significantly lower than in emptying state (SMD=-2.48, 95% CI: -4.37--0.59, P=0.000). D1 cm3 and D2 cm3 showed no significant difference (P=0.000, 0.000). D2 cm3 to the rectum in filling state was greater than in emptying state (SMD=0.39, 95% CI: 0.06-0.72, P=0.257). D50 and D1 cm3 showed no significant difference (P=0.105, 0.005). D2 cm3 to the sigmoid colon in filling state was greater than in emptying state (SMD=0.81, 95% CI: 0.50-1.12, P=0.648). D50 and D1 cm3 showed no significant difference (P=0.039, 0.000). D1 cm3 and D2 cm3 to the small bowel in filling state was lower than in emptying state (SMD=-3.28, 95% CI: -5.61--0.95, P=0.000 and SMD=-2.98, 95% CI: -4.68--1.28, P=0.000). D50 showed no significant difference (P=0.008). When sensitivity analyses were performed by the sequential dropping of a single study, differences were observed when the study of Patra et al was excluded. Conclusions In intracavitary brachytherapy of cervical cancer, the dose distribution to the bladder and small bowel in filling bladder state were lower than those in emptying bladder state, the results of sigmoid colon and rectum were just opposite. Confined by article quality and quantity, further evaluations in adequately powered large control trail are needed to confirm these findings. Key words: Cervical neoplasms/intracavitary brachytherapy; Bladder status; Meta-analysis