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.

Methods and Materials

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 D₉₀/D₉₈ and modeled bladder/rectum D_2cc were computed using the composite EQD2 dose distributions of all the treatment combinations.

Results

If appropriate combinations of the treatment plans were selected on the basis of the CS doses and the HR-CTV sizes, the D₉₀/D₉₈ 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 D₉₀/bladder D_2cc/rectum D_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.

Conclusion

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