The impact of bladder volume on dosimetric outcomes in VMAT for cervical cancer patients after surgery.

Objective: This study aimed to investigate the impact of bladder volume on dosimetric outcomes of organs at risk (OARs) in postoperative volumetric-modulated arc therapy (VMAT) for patients with cervical cancer.

Methods: The study included 71 cervical cancer patients who received radical hysterectomy and postoperative VMAT between January 2020 and January 2023. Patients were divided into 3 groups according to average bladder volume observed in computed tomography simulation positioning images: Group A (<300 mL), Group B (300-500 mL), and Group C (≥500 mL). The study compared dosimetric parameters(V₃₀, V₄₀, V₄₅, and D_2cc) for OARs like the bladder, rectum, small intestine, and sigmoid colon, as well as the incidence of radiation cystitis and proctitis among these groups.

Results: The median follow-up of the cohort was 33 months, with a median patient age of 48 years. Group A demonstrated the highest V₄₀ and V₄₅ values for the bladder (p<0.05). Conversely, Group C displayed the highest values for the V₄₀ and V₄₅ of the rectum, as well as the V₄₅ and D_2cc of the sigmoid colon (p<0.05). No statistically significant differences were observed in the incidence of acute radiation cystitis and radiation cystitis among the 3 groups. Significant difference was observed in the incidence rates of late radiation cystitis (p<0.05) and radiation proctitis (p<0.05) among the 3 groups. Group A exhibited the highest prevalence of late radiation cystitis, whereas Group C demonstrated the highest prevalence of late radiation proctitis.

Conclusion: Bladder volume significantly affects dosimetry of the bladder, rectum, and sigmoid colon in postoperative VMAT for cervical cancer patients. A recommended bladder volume of 300-500 mL helps reduce radiation-induced cystitis and proctitis.