Dose-volume histogram analysis of composite EQD2 dose distributions using the central shielding technique in cervical cancer radiotherapy

详细信息    查看全文

• 作者：Tomoaki Tamaki¹ ; ² ; ³ ; ^{tamakit@fmu.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Shin-ei Noda² ; Tatsuya Ohno² ; Yu Kumazaki³ ; Shingo Kato³ ; Takashi Nakano²
• 关键词：External-beam radiotherapy ; Intracavitary brachytherapy ; Whole-pelvis irradiation ; Cervical cancer ; Central shielding technique
• 刊名：Brachytherapy
• 出版年：2016
• 出版时间：September-October 2016
• 年：2016
• 卷：15
• 期：5
• 页码：598-606
• 全文大小：1685 K

文摘

To analyze the dose–volume histogram of the central shielding technique for cervical cancer radiotherapy by computing the composite three-dimensional EQD2 dose distributions of external-beam radiotherapy plus intracavitary brachytherapy.

d="absSec_2">Methods and Materials

d="abspara0015">On a phantom, three patterns of high-risk clinical target volume (HR-CTV) with right–left diameters of 3, 4, and 5 cm were created using clinical data. Four patterns of combinations of whole-pelvis irradiation plus “pelvis irradiation using the central shielding technique” (CS) (shielding width, 3 or 4 cm) were created: 20 Gy/10 fractions + 30 Gy/15 fractions, 30 Gy/15 fractions + 20 Gy/10 fractions, 40 Gy/20 fractions + 10 Gy/5 fractions, and 50 Gy/25 fractions + 0 Gy. The intracavitary brachytherapy plan was set as 24 Gy/4 fractions prescribed to the Point A. The HR-CTV m>Dm>₉₀/m>Dm>₉₈ and modeled bladder/rectum m>Dm>_2cc were computed using the composite EQD2 dose distributions of all the treatment combinations.

d="absSec_3">Results

d="abspara0020">If appropriate combinations of the treatment plans were selected on the basis of the CS doses and the HR-CTV sizes, the m>Dm>₉₀/m>Dm>₉₈ of HR-CTV 3 cm, HR-CTV 4 cm, and HR-CTV 5 cm were 89.7 Gy/80.6 Gy, 77.3 Gy/72.0 Gy, and 73.0 Gy/69.2 Gy in the case of CS width 3 cm, respectively; and 86.2 Gy/76.0 Gy, 73.3 Gy/67.6 Gy, and 70.9 Gy/67.1 Gy in the case of CS width 4 cm, respectively. The contributions of CS to the HR-CTV m>Dm>₉₀/bladder m>Dm>_2cc/rectum m>Dm>_2cc values were 24–56%/28–32%/9% of the CS plan doses for shielding width of 3 cm and were 13–35%/11–16%/5–6% for shielding width of 4 cm.

d="absSec_4">Conclusion

d="abspara0025">The dose contributions of CS were variable but not negligible when analyzing the total doses delivered to the HR-CTV.