Zhang Li, Johnson Julian, Gottschalk Alexander R, Chang Albert J, Hsu I-Chow, Roach Mack, Seymour Zachary A
Helen Diller Family Comprehensive Cancer Center, University of California at San Francisco, San Francisco, California; Department of Epidemiology and Biostatistics, University of California at San Francisco, San Francisco, California.
Department of Radiation Oncology, University of California at San Francisco, San Francisco, California.
Pract Radiat Oncol. 2017 Mar-Apr;7(2):e109-e116. doi: 10.1016/j.prro.2016.07.004. Epub 2016 Jul 17.
The purpose of this study was to evaluate a receiver operating characteristic (ROC) curve method to determine dose thresholds with late genitourinary (GU) toxicity after stereotactic body radiation therapy for prostate cancer.
Seventy-eight patients diagnosed with low- to intermediate-risk prostate cancer and treated with stereotactic body radiation therapy alone were reviewed retrospectively. All patients received a total dose of 38 Gy in 4 fractions with a planning target volume expansion of 2 mm. GU toxicity was documented according to the Common Terminology Criteria for Adverse Events, version 4. ROC analysis applied on a logistic regression model was used to determine optimal dosimetric parameters for GU toxicity.
The median age at treatment was 69 years with a median prostate volume of 46.2 mL. The median prescription isodose line was 67% (interquartile range, 65, 70). The median clinical follow-up was 35.49 months. Late grade 1, 2, and 3 GU toxicity occurred in 21.8%, 19.2%, and 2.6% of cases, respectively. Late grade 2+ GU toxicity was associated with prescription to isodose line (P = .009) and normalized volumes for heterogeneity ≥46 Gy. The ROC method successfully produced thresholds for dose-volume recommendations for both prostate and urethra, including normalized prostate volumes from 46 to 50 Gy, such as volume of target tissue receiving 46% of the prescribed dose (V46) Gy of 36.7% (sensitivity, 71%; specificity, 61%; area under the curve, 0.67) with an associated probability of late GU grade 2+ toxicity of 21%.
Intraprostatic heterogeneity should be controlled with potential thresholds at V46 Gy <36.7%, V48 Gy <21%, and V50 Gy <9.5% of the normalized prostate volume to keep late grade 2+ GU toxicity ≤20% with 4-fraction schemes. This may be facilitated with a higher prescription isodose line (>69%).
本研究旨在评估一种接受者操作特征（ROC）曲线方法，以确定前列腺癌立体定向体部放射治疗后晚期泌尿生殖系统（GU）毒性的剂量阈值。
回顾性分析78例诊断为低至中度风险前列腺癌且仅接受立体定向体部放射治疗的患者。所有患者分4次接受总剂量38 Gy，计划靶体积外放2 mm。根据不良事件通用术语标准第4版记录GU毒性。应用逻辑回归模型进行ROC分析，以确定GU毒性的最佳剂量学参数。
治疗时的中位年龄为69岁，前列腺中位体积为46.2 mL。中位处方等剂量线为67%（四分位间距，65，70）。中位临床随访时间为35.49个月。晚期1级、2级和3级GU毒性分别发生在21.8%、19.2%和2.6%的病例中。晚期2级及以上GU毒性与处方等剂量线（P = .009）以及归一化体积的异质性≥46 Gy相关。ROC方法成功得出了前列腺和尿道剂量-体积推荐的阈值，包括46至50 Gy的归一化前列腺体积，例如接受46%处方剂量（V46）Gy的靶组织体积为36.7%（敏感性，71%；特异性，61%；曲线下面积，0.67），晚期GU 2级及以上毒性的相关概率为21%。
对于4分次方案，应将前列腺内异质性控制在归一化前列腺体积的V46 Gy <36.7%、V48 Gy <21%和V50 Gy <9.5%的潜在阈值，以使晚期2级及以上GU毒性≤20%。较高的处方等剂量线（>69%）可能有助于实现这一点。
