A comparative dosimetric analysis of virtual stereotactic body radiotherapy to high-dose-rate monotherapy for intermediate-risk prostate cancer

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• 作者：Daniel E. Spratt ; Lawrence M. Scala ; Michael Folkert ; Laszlo Voros ; Gil¡¯ad N. Cohen ; Laura Happersett ; Evangelia Katsoulakis ; Michael J. Zelefsky ; Marisa A. Kollmeier ; Yoshiya Yamada
• 关键词：Prostate cancer ; Brachytherapy ; High-dose rate ; Stereotactic body radiotherapy ; Dosimetry
• 刊名：Brachytherapy
• 出版年：2013
• 出版时间：September-October, 2013
• 年：2013
• 卷：12
• 期：5
• 页码：428-433
• 全文大小：362 K

文摘

Purpose

Stereotactic body radiotherapy (SBRT) is being used with increasing frequency as definitive treatment of early stage prostate cancer. Much of the justification for its adoption was derived from earlier clinical results using high-dose-rate (HDR) brachytherapy. We determine whether HDR's dosimetry can be achieved by virtual SBRT.

Methods and Materials

Patients with intermediate-risk prostate cancer on a prospective trial evaluating the efficacy of HDR monotherapy treated to dose of 9.5 Gy ¡Á 4 fractions were used for this study. A total of 5 patients were used in this analysis. Virtual SBRT plans were developed to reproduce the planning target volume (PTV) HDR dose distributions. Both normal tissue- and PTV-prioritized plans were generated.

Results

From the normal tissue-prioritized plan, HDR and virtual SBRT achieved similar PTV V₁₀₀ (93.8 % vs. 93.1 % , p = 0.20) and V₁₅₀ (40.3 % vs. 42.9 % , p = 0.69) coverage. However, the PTV V₂₀₀ was not attainable with SBRT (15.2 % vs. 0.0 % , p < 0.001). The rectal D_max was significantly lower with HDR (94.2 % vs. 99.42 % , p = 0.05). The rectal D_{2 cc} was also lower (60.8 % vs. 71.1 % , p = 0.07). Difference in D_{1 cc} urethral dose was not significantly different (87.7 % vs. 75.2 % , p = 0.33). Comparing the PTV-prioritized plans, the rectal D_max (94.2 % vs. 111.1 % , p = 0.05) and mean dose (27.1 % vs. 33.3 % , p = 0.03) were significantly higher using SBRT, and the rectal D_{2 cc} was higher using SBRT (60.8 % vs. 81.8 % , p = 0.07).

Conclusions

HDR achieves significantly higher intraprostatic doses while achieving a lower maximum rectal dose compared with our virtual SBRT treatment planning. Future studies should compare clinical outcomes and toxicity between these modalities.