Abstract
BackgroundUnderstanding intra-fractional prostate motions is crucial for stereotactic body radiation therapy (SBRT). No studies have focused on the intra-fractional prostate motions during re-irradiation with SBRT. The objective was to evaluate these translational and rotational motions in primary treated patients and in the context of re-irradiation.MethodsFrom January 2011 to March 2020, 162 patients with histologically proven prostate cancer underwent prostate SBRT, including 58 as part of a re-irradiation treatment. We used the continuous coordinates of the fiducial markers collected by an orthogonal X-ray dual-image monitoring system. The translations and rotations of the prostate were calculated. Prostate deviations representing overall movement was defined as the length of the 3D-vectors.ResultsA total of 858 data files were analyzed. The deviations over time in the group of primary treated patients were significantly larger than that of the group of re-irradiation, leading to a mean deviation of 2.73 mm (SD =1.00) versus 1.90 mm (SD =0.79), P<0.001. In the re-irradiation group, we identified displacements of -0.05 mm (SD =1.53), 0.20 mm (SD =1.46); and 0.42 mm (SD =1.24) in the left-right, superior-inferior and anterior-posterior planes. Overall, we observed increasing deviations over the first 30 min followed by a stabilization related to movements in the three translational axes.ConclusionThis is the first study to focus on intrafraction prostate motions in the context of re-irradiation. We observed that intra-fraction prostate motions persisted in the setting of re-irradiation, although they showed a significant reduction when compared with the first irradiation. These results will help to better estimate random errors during SBRT treatment of intra-prostatic recurrence after irradiation.
Highlights
With an estimated 1.4 million new cases and 375,000 deaths worldwide, prostate cancer was the second most frequent cancer and the fifth leading cause of cancer death among men in 2020 [1]
The patients were divided into two different population groups, with the first group comprising patients with an indication for stereotactic body radiation therapy (SBRT) as a treatment for localized prostate disease who had never received local treatment, and the second group comprising patients treated with SBRT for an intraprostatic recurrence after the first radiation of the external beam radiation therapy (EBRT) type or brachytherapy
After excluding five patients who objected to the use of their medical data, the study population consisted of 162 patients whose median age at enrollment was 73 years old
Summary
With an estimated 1.4 million new cases and 375,000 deaths worldwide, prostate cancer was the second most frequent cancer and the fifth leading cause of cancer death among men in 2020 [1]. Radiation therapy has been validated as a standard treatment for localized prostate cancer [2, 3] and several radiation therapy methods have been developed. Studies have shown that by delivering high doses of radiation per session, stereotactic radiation therapy (SBRT) provides a control similar to that obtained with standard techniques [4,5,6]. An intra-prostatic recurrence is the site of first recurrence after normal fractionated radiation therapy [7]. Traditional treatment options for the local treatment of intra-prostatic recurrence include radical prostatectomy, brachytherapy, cryotherapy, and high-intensity focused ultrasound (HIFU) [2]. Understanding intra-fractional prostate motions is crucial for stereotactic body radiation therapy (SBRT). No studies have focused on the intra-fractional prostate motions during re-irradiation with SBRT. The objective was to evaluate these translational and rotational motions in primary treated patients and in the context of re-irradiation
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