Impact of bladder volume on treatment planning and clinical outcomes of radiotherapy for patients with cervical cancer

OBJECTIVE: This study aimed to investigate the impact of bladder volume on treatment planning and clinical outcomes of radiotherapy for patients with cervical cancer. MATERIALS AND METHODS: One hundred and sixty-six patients with locally advanced cervical cancer were selected in this retrospective study. The patients were divided into four groups according to their average bladder volume during radiotherapy (external beam radiation therapy and intracavitary brachytherapy): group A: V<100 mL, group B: 100 mL≤V≤150 mL, group C: 150 mL<V≤200 mL, group D: V>200 mL. The bladder volume and the cumulative dose to planning target (D90), bladder (D2cc), rectum (D2cc), and sigmoid (D2cc) were calculated using the treatment planning system. Treatment outcomes including late adverse events (the maximum grade of radiation-induced proctitis and cystitis), the objective response rate of tumor and lymph node, overall survival (OS), and progression-free survival (PFS) were collected. Additionally, the correlation between bladder volume and the irradiated dose of organs at risk and treatment outcomes was analyzed. RESULTS: The median follow-up time was 28 months. The D90 and D2cc of the rectum in group A were the highest (P<0.05). The D2cc of the bladder in group D was the highest (P<0.05). There was no significant difference in the tumor and lymph node regression rate, OS, and PFS among the groups. The difference in the late radiation-induced proctitis and cystitis maximum grade among the four groups was statistically significant (P<0.001, P=0.022, respectively), with group A the most serious and group B the mildest. CONCLUSION: For patients with cervical cancer, the bladder volume significantly affected the delivered dose to target, rectum, and bladder. When the bladder volume range was 100–150 mL, the rate of late radiation-induced proctitis and cystitis was low and the degree of reaction was mild. This is thought to be the optimum bladder volume for patients with cervical cancer during radiotherapy.