Re-planning for daily CT-image guided proton prostate cancer treatment

What is it about?

This study reported the effectiveness of the re-planning protocol for proton prostate cancer treatment to spare the rectal dose based on the analyses of about 1500 sets daily CT-images acquired by in-room CT image guidance. Daily movements of the anterior rectal wall were studied by referring the daily CT-images and the simulator CT-images consecutively. We searched the optimal reference period when the daily deviation of the rectal shape from the reference reduced over the rest of the treatment, and found that the re-planning with daily CT-images acquired after 10 days passed was effective to spare the rectal dose in particular for such a patient that the daily anterior rectal wall around the seminal vesicles tends to move toward the anterior side. We also demonstrated an empirical method to monitor daily rectal dose parameters and identify patients with over dose condition during the early period of the treatment.

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Why is it important?

Our data demonstrate that the daily movement of the rectal anterior side tends to move toward the anterior side, which results in a rectal overdose, and the mean of the movement gradually decreases with the passage of days. In such cases, re-planning with the reference CT after 10 days is effective to spare the rectal dose.

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