論文

Purpose: Rectal complications in radiotherapy for cervical cancer can highly affect quality of life and correlate with rectal dose. Vaginal gauze packing (VP) and rectal retraction (RR) are widely used for rectal dose reduction in high-dose-rate brachytherapy. We aimed to perform a dosimetric comparison of these two methods for three-dimensional image-guided adaptive brachytherapy. Material and methods: We retrospectively examined 50 patients with cervical cancer treated with definitive radiotherapy, including intra-cavitary brachytherapy, performed with VP and RR. We extracted two fractions for each patient: one fraction with VP and the next fraction with RR, and then compared dose-volume parameters. In total, 50 fractions each were analyzed in VP and RR groups. Dose to 90% (D90) of high-risk clinical target volume (HR-CTV), and minimum dose to most exposed 2.0 cm3 of other organs at risk (D2cm3) for the rectum and bladder were determined from planning computed tomography. Results: There were no significant differences between VP and RR in D90 of HR-CTV (mean: 7.479 Gy and 7.652 Gy, respectively, p = 0.172). The D2cm3 values for the rectum (mean: 4.234 Gy vs. 4.627 Gy, p = 0.008) and bladder (mean: 5.959 Gy vs. 6.690 Gy, p < 0.001) were significantly lower with VP compared with RR. Conclusions: VP reduced the dose to the rectum and bladder when compared with RR without impairing the dose to CTV.

Objective: To evaluate the efficiency of high-energy photons for mitigating alopecia due to whole-brain irradiation (WBRT). Methods: Planning CT data from 10 patients who received WBRT were collected. We prepared 4 WBRT plans that used 6 or 15 MV photon beams, with or without use of a field-in-field (FiF) technique, and compared outcomes using a treatment planning system. The primary outcome was dose parameters to the scalp, including the mean dose, maximum dose, and dose received to 50% scalp (D50%). Secondary outcomes were minimum dose to the brain surface. Results: Using FiF, the mean doses were 24.4-26.0 and 22.4-24.1 Gy, and the maximum doses were 30.5-32.1 and 28.5-30.8 Gy for 6 and 15 MV photon beams, respectively. Without FiF, the mean doses were 24.6-26.9 and 22.6-24.5 Gy, and the maximum doses were 30.8-34.6 and 28.6-32.4 Gy for 6 and 15 MV photon beams. The 15 MV plan resulted in a lower scalp dose for each dose parameter (p < 0.001). Using FiF, the minimum doses to the brain surface for the 6 and 15 MV plans were 28.9 ± 0.440 and 29.0 ± 0.557 Gy, respectively (p = 0.70). Without FiF, the minimum doses to the brain surface for the 6 and 15 MV plans were 28.9 ± 0.456 and 29.0 ± 0.529, respectively (p = 0.66). Conclusion: Compared with the 6 MV plan, the 15 MV plan achieved a lower scalp dose without impairing the brain surface dose. Advances in knowledge: High-energy photon WBRT may mitigate alopecia of patients who receiving WBRT.