Dose to bone marrow using IMRT techniques in prostate cancer patients

Area of Science:

• Radiation oncology
• Medical physics
• Cancer treatment

Background:

• Prostate cancer radiotherapy aims to maximize tumor control while minimizing side effects.
• Intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3-D CRT) are advanced techniques for delivering radiation.
• Understanding bone marrow dose distribution is crucial for assessing secondary leukemia risk.

Purpose of the Study:

• To compare active bone marrow dose distribution between IMRT and 3-D CRT for prostate cancer.
• To identify optimization criteria for IMRT to minimize secondary leukemia risk.
• To evaluate dose distribution differences for both whole-pelvis and prostate-only treatments.

Main Methods:

• Calculated mean bone marrow doses for ten prostate cancer patients treated with whole-pelvis IMRT.
• Compared IMRT plans to 3-D CRT plans for the same patients.
• Simulated prostate-only IMRT and 3-D CRT plans.
• Measured extrapelvic bone marrow dose using thermoluminescent diodes in a phantom.

Main Results:

• IMRT plans reduced high doses to rectum, bladder, and small bowel compared to 3-D CRT.
• For pelvic treatments, IMRT decreased high doses (>20 Gy) to os coxae but increased moderate doses (10-20 Gy).
• IMRT plans showed higher leakage doses to extrapelvic sites (factor of 2) compared to 3-D CRT.

Conclusions:

• Significant differences exist in bone marrow dose-volume histograms between IMRT and 3-D CRT.
• Dose inhomogeneity, rather than mean dose, is critical for reducing leukemia risk.
• Scattered low doses to distant bone marrow sites may be more significant than high-dose pelvic volumes.