Equivalent uniform RBE-weighted dose in eye plaque brachytherapy
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作者:
Chvetsov, Alexei V.
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Univ Washington, Dept Radiat Oncol, Seattle, WA USA
Univ Washington, Dept Radiat Oncol, 1959 NE Pacific St, Seattle, WA 98004 USAUniv Washington, Dept Radiat Oncol, Seattle, WA USA
Chvetsov, Alexei V.
[1
,2
]
机构:
[1] Univ Washington, Dept Radiat Oncol, Seattle, WA USA
[2] Univ Washington, Dept Radiat Oncol, 1959 NE Pacific St, Seattle, WA 98004 USA
BackgroundBrachytherapy for ocular melanoma is based on the application of eye plaques with different spatial dose nonuniformity, time-dependent dose rates and relative biological effectiveness (RBE). PurposeWe propose a parameter called the equivalent uniform RBE-weighted dose (EUDRBE) that can be used for quantitative characterization of integrated cell survival in radiotherapy modalities with the variable RBE, dose nonuniformity and dose rate. The EUDRBE is applied to brachytherapy with 125I eye plaques designed by the Collaborative Ocular Melanoma Study (COMS). MethodsThe EUDRBE is defined as the uniform dose distribution with RBE = 1 that causes equal cell survival for a given nonuniform dose distribution with the variable RBE > 1. The EUDRBE can be used for comparison of cell survival for nonuniform dose distributions with different RBE, because they are compared to the reference dose with RBE = 1. The EUDRBE is applied to brachytherapy with 125I COMS eye plaques that are characterized by a steep dose gradient in tumor base-apex direction, protracted irradiation during time intervals of 3-8 days, and variable dose-rate dependent RBE with a maximum of about 1.4. The simulations are based on dose of 85 Gy prescribed to the farthest intraocular extent of the tumor (tumor apex). To compute the EUDRBE in eye plaque brachytherapy and correct for protracted irradiation, the distributions of physical dose have been converted to non-uniform distributions of biologically effective dose (BED) to include the biological effects of sublethal cellular repair, Our radiobiological analysis considers the combined effects of different time-dependent dose rates, spatial dose non-uniformity, dose fractionation and different RBE and can be used to derive optimized dose regimens brachytherapy. ResultsOur simulations show that the EUDRBE increases with the prescription depths and the maximum increase may achieve 6% for the tumor height of 12 mm. This effect stems from a steep dose gradient within the tumor that increases with the prescription depth. The simulations also show that the EUDRBE increase may achieve 12% with increasing the dose rate when implant duration decreases. The combined effect of dose nonuniformity and dose rate may change the EUDRBE up to 18% for the same dose prescription of 85 Gy to tumor apex. The absolute dose range of 48-61 Gy (RBE) for the EUDRBE computed using 4 or 5 fractions is comparable to the dose prescriptions used in stereotactic body radiation therapy (SBRT) with megavoltage X-rays (RBE = 1) for different cancers. The tumor control probabilities in SBRT and eye plaque brachytherapy are very similar at the level of 80% or higher that support the hypothesis that the selected approximations for the EUDRBE are valid. ConclusionsThe computed range of the EUDRBE in 125I COMS eye plaque brachytherapy suggests that the selected models and hypotheses are acceptable. The EUDRBE can be useful for analysis of treatment outcomes and comparison of different dose regimens in eye plaque brachytherapy.
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Univ Calif Los Angeles, Dept Radiat Oncol, Los Angeles, CA USAUniv Calif Los Angeles, Dept Radiat Oncol, Los Angeles, CA USA
Ramesh, Pavitra
Ruan, Dan
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Univ Calif Los Angeles, Dept Radiat Oncol, Los Angeles, CA USAUniv Calif Los Angeles, Dept Radiat Oncol, Los Angeles, CA USA
Ruan, Dan
Liu, S. John
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Univ Calif San Francisco, Dept Radiat Oncol, San Francisco, CA USAUniv Calif Los Angeles, Dept Radiat Oncol, Los Angeles, CA USA
Liu, S. John
Seo, Youngho
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Univ Calif San Francisco, Dept Radiol & Biomed Imaging, San Francisco, CA USAUniv Calif Los Angeles, Dept Radiat Oncol, Los Angeles, CA USA
Seo, Youngho
Braunstein, Steve
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Univ Calif San Francisco, Dept Radiat Oncol, San Francisco, CA USAUniv Calif Los Angeles, Dept Radiat Oncol, Los Angeles, CA USA
Braunstein, Steve
Sheng, Ke
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Univ Calif San Francisco, Dept Radiat Oncol, San Francisco, CA USA
UCSF Radiat Oncol, 1600 Divisadero St, San Francisco, CA 94143 USAUniv Calif Los Angeles, Dept Radiat Oncol, Los Angeles, CA USA
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Shanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R ChinaShanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R China
Wang, Weiwei
Huang, Zhijie
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Shanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R ChinaShanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R China
Huang, Zhijie
Sheng, Yinxiangzi
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Shanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R ChinaShanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R China
Sheng, Yinxiangzi
Zhao, Jingfang
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Shanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R China
Fudan Univ, Shanghai Canc Ctr, Dept Radiat Oncol, Shanghai, Peoples R ChinaShanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R China
Zhao, Jingfang
Shahnazi, Kambiz
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Shanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R ChinaShanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R China
Shahnazi, Kambiz
Zhang, Qing
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Shanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Radiat Oncol, 4365 Kangxin Rd, Shanghai 201315, Peoples R ChinaShanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R China
Zhang, Qing
Jiang, Guoliang
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Shanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Radiat Oncol, 4365 Kangxin Rd, Shanghai 201315, Peoples R ChinaShanghai Engn Res Ctr Proton & Heavy Ion Radiat T, Shanghai Proton & Heavy Ion Ctr, Dept Med Phys, Shanghai 201315, Peoples R China