OBJECTIVES To propose a follow-up strategy for desmoid-type fibromatosis (DF) based on tumor growth behavior and the signal on T2-weighted MRI. METHODS We retrospectively reviewed 296 MRI studies of 34 patients with histologically proven DF. In each study, tumor volume and T2 signal relatively normal striated muscle were assessed. Volume variation and monthly growth rates were analyzed to determine lesion growth behavior (progressing versus stable/regressing lesions). Growth behavior was correlated with T2 signal, tumor location, β-catenin status, treatment strategy, and follow-up duration. Interobserver variability of volume measurements and interobserver measurement variation ratio were assessed. RESULTS There were 25 women and 9 men with a mean age of 39.9 ± 19 (4-73) years. Mean follow-up time in the patients included was 55 ± 41 (12-148) months. In progressing lesions, the mean average monthly growth ratio was 10.9 ± 9.2 (1.1-42.5) %. Interobserver variability of volume measurements was excellent (ICC = 0.96). Mean interobserver measurement variation ratio was 20.4 ± 23.6%. The only factor correlated with tumor growth behavior was T2 signal ratio (p < 0.0001). Seventeen out of 34 (50%) patients presented a signal change over the threshold of 1 during follow-up. There were five occurrences of secondary growth after a period of stability with a mean delay until growth of 38.2 ± 44.2 (17-116) months. CONCLUSION DF growth rate was quantitatively assessed. A threshold for volume variation detection was established. DF growth behavior was significantly related to T2 signal. An evidence-based follow-up strategy is proposed. KEY POINTS • In progressing desmoid fibromatosis, the mean average monthly growth ratio was 10.9 ± 9.2%. • Lesions with muscle/tumor T2 signal ratios lower than 1 tended to be stable or regress over time. • Given the interobserver measurement variability and MRI in-plane spatial resolution, a variation higher than 42.6% in tumor volume is required to confirm punctual progression.

中文翻译：

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基于证据的MR成像策略治疗类胶质纤维瘤病。

目的根据肿瘤生长行为和T2加权MRI的信号，提出针对类胶质纤维瘤病（DF）的随访策略。方法我们回顾性分析了34例经组织学证实为DF的296例MRI研究。在每项研究中，评估了相对正常的横纹肌的肿瘤体积和T2信号。分析体积变化和月增长率，以确定病变的生长行为（病变进展与稳定/退化）。生长行为与T2信号，肿瘤位置，β-catenin状态，治疗策略和随访时间相关。评估了观察者间的体积测量变异性和观察者间的测量变异率。结果有25名女性和9名男性，平均年龄为39.9±19（4-73）岁。纳入患者的平均随访时间为55±41（12-148）个月。在进行性病变中，平均月平均增长率为10.9±9.2（1.1-42.5）％。观察者之间的体积测量差异非常好（ICC = 0.96）。观察者之间的平均测量差异率为20.4±23.6％。与肿瘤生长行为相关的唯一因素是T2信号比（p <0.0001）。34名患者中有17名（50％）在随访期间信号变化超过阈值1。稳定期后平均发生延迟，直到生长38.2±44.2（17-116）个月后，出现了二次生长的五次。结论定量评估了DF的生长速率。建立了体积变化检测的阈值。DF的生长行为与T2信号显着相关。提出了基于证据的跟踪策略。要点•在进行性胶质纤维瘤病的进展中，平均月平均增长率为10.9±9.2％。•肌肉/肿瘤T2信号比低于1的病变往往会稳定或随时间消退。•考虑到观察者之间的测量差异和MRI平面内空间分辨率，需要确认肿瘤体积大于42.6％的变化才能确认穿刺点的进展。