Radiotherapy in a patient with rectal cancer and pelvic kidney: a dosimetric study

INTRODUCTION: Pelvic kidney is an important treatment challenge in pelvic malignancies. This study investigated the most appropriate treatment in the presence of simultaneous pelvic kidney in patients with rectal cancer.
METHODS: This study used computed tomography images of postoperative radiotherapy planning in a male patient with rectal cancer. Coplanar intensity-modulated, non-coplanar intensity-modulated, and volumetric-modulated arc radiotherapy rectal cancer planning was performed with six different scenarios based on tumor location and lymph node status; a dosimetric comparison was then performed.
RESULTS: In a patient with rectal cancer and pelvic kidney, where the external iliac lymph nodes were not included in the radiation field, it was determined that, regardless of rectal tumor localization, optimal ≤45 Gy radiotherapy planning could only be performed with the volumetric-modulated arc therapy technique. In the same scenario, optimal ≤50.4 Gy radiotherapy planning could only be performed in a distally localized rectal tumor and with the volumetric-modulated arc therapy technique. In contrast, when the external iliac lymph nodes were included in the radiation field for the same patient, regardless of rectal tumor localization, no radiotherapy technique ≤45 Gy could protect the pelvic kidney.
DISCUSSION AND CONCLUSION: In patients with locally advanced rectal cancer and pelvic kidney, oncologic treatment (either radiotherapy first or surgery first) should be decided based on the available radiotherapy technique, lymph node status of rectal cancer, and tumor localization.