Adjuvant Radiotherapy in Bladder Cancers: A Dosimetric Study Focusing on Ileal Conduit Sparing

Area of Science:

• Radiation Oncology
• Medical Physics
• Urologic Oncology

Background:

• Adjuvant radiotherapy (RT) is used after radical cystectomy with ileal conduit (IC) reconstruction.
• Accurate dosimetry for the IC and other organs at risk (OARs) is crucial for minimizing toxicity.
• Comparing different RT techniques is essential for optimizing treatment delivery.

Purpose of the Study:

• To compare the dosimetry of the ileal conduit (IC) and other organs at risk (OARs) between 3-dimensional conformal radiotherapy (3DCRT) and volumetric modulated arc therapy (VMAT).
• To evaluate target volume coverage and OAR doses in patients undergoing adjuvant RT post-cystectomy with IC.

Main Methods:

• A prospective cohort of 20 patients undergoing adjuvant RT post-cystectomy with IC were included.
• CT datasets were used to delineate target volumes and OARs, including the IC and ileal stoma.
• Three RT plans were generated: 3DCRT without stoma shielding (3DCRT_N), 3DCRT with stoma shielding (3DCRT_S), and VMAT.

Main Results:

• VMAT significantly reduced the median IC V50Gy (17.05 cc) compared to 3DCRT_N (38.81 cc) and 3DCRT_S (35.62 cc).
• VMAT achieved significantly lower Dmax doses to the ileal stoma (24.22 Gy) compared to 3DCRT_N (35.32 Gy) and 3DCRT_S (27.57 Gy).
• VMAT demonstrated superior dosimetry for uretero-ileal anastomosis, bowel, and rectal OARs compared to both 3DCRT techniques.

Conclusions:

• Volumetric modulated arc therapy (VMAT) effectively spares the ileal conduit (IC) and ileal stoma without compromising planning target volume (PTV) coverage.
• 3DCRT with ileal stoma shielding compromises PTV coverage and is less effective in sparing the IC.
• VMAT offers dosimetric advantages that may reduce anastomotic and mucosal complications, warranting further clinical evaluation.