Roeloffzen Ellen M, Crook Juanita, Monninkhof Evelyn M, McLean Michael, van Vulpen Marco, Saibishkumar Elantholi P
Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands.
Brachytherapy. 2012 Jul-Aug;11(4):256-64. doi: 10.1016/j.brachy.2011.12.011. Epub 2012 Feb 17.
Acute urinary retention (AUR) after (125)I prostate brachytherapy has a negative impact on quality of life. Recently, the authors developed a nomogram to predict the risk of AUR preoperatively. The aim of this study was to assess the external validity of the nomogram.
The nomogram was initially developed on 714 patients treated with (125)I prostate brachytherapy at the University Medical Center Utrecht, the Netherlands. Predictive factors included in the nomogram were prostate volume, international prostate symptom score, neoadjuvant hormonal treatment, and prostate protrusion. For external validation, the data of 715 consecutive patients treated between January 2003 and July 2008 at the Princess Margaret Hospital, Toronto, were used. The performance of the nomogram was evaluated by discrimination (ability to distinguish between patients who develop AUR yes or no) and calibration (agreement between observed and predicted numbers of AUR).
Of the 715 patients treated at the Princess Margaret Hospital, 67 patients (9.4%) developed AUR compared with 8.0% in the University Medical Center Utrecht cohort. In the validation data set, the discriminatory ability of the nomogram was good (receive operating characteristic area: 0.86; 95% confidence interval: 0.82-0.91), and comparable to the derivation data set (receive operating characteristic area: 0.82; 95% confidence interval: 0.77-0.88). Comparison between the predicted risks and the observed frequencies of AUR showed underestimation of the nomogram in the validation data set for high AUR risks values. Still, the negative predictive value for the risk of AUR, using a cutoff value of 5%, was high (98.1%).
External validation of the nomogram shows adequate discrimination of patients with and without AUR. Therefore, the nomogram can aid in individualized treatment decision making.
¹²⁵I前列腺近距离放射治疗后急性尿潴留（AUR）对生活质量有负面影响。最近，作者开发了一种列线图以术前预测AUR风险。本研究的目的是评估该列线图的外部有效性。
该列线图最初是基于荷兰乌得勒支大学医学中心接受¹²⁵I前列腺近距离放射治疗的714例患者开发的。列线图中纳入的预测因素包括前列腺体积、国际前列腺症状评分、新辅助激素治疗和前列腺突出情况。为进行外部验证，使用了2003年1月至2008年7月期间在多伦多玛格丽特公主医院接受治疗的715例连续患者的数据。通过区分能力（区分发生AUR与否的患者的能力）和校准（AUR的观察值与预测值之间的一致性）来评估列线图的性能。
在玛格丽特公主医院接受治疗的715例患者中，67例（9.4%）发生了AUR，而在乌得勒支大学医学中心队列中这一比例为8.0%。在验证数据集中，列线图的区分能力良好（受试者工作特征曲线下面积：0.86；95%置信区间：0.82 - 0.91），与推导数据集相当（受试者工作特征曲线下面积：0.82；95%置信区间：0.77 - 0.88）。AUR预测风险与观察频率之间的比较显示，在验证数据集中，对于高AUR风险值，列线图存在低估情况。不过，使用5%的截断值时，AUR风险的阴性预测值较高（98.1%）。
列线图的外部验证表明其对有或无AUR的患者有足够的区分能力。因此，该列线图有助于个体化治疗决策。
