Is interim 18F-fluoride PET/CT a predictor of outcomes after radium-223 therapy?

Abstract Objective: To determine whether an interim 18F-fluoride positron-emission tomography/computed tomography (PET/CT) study performed after the third cycle of radium-223 dichloride (223RaCl2) therapy is able to identify patients that will not respond to treatment. Materials and Methods: We retrospectively reviewed 34 histologically confirmed cases of hormone-refractory prostate cancer with bone metastasis in patients submitted to 223RaCl2 therapy. All of the patients underwent baseline and interim 18F-fluoride PET/CT studies. The interim study was performed immediately prior to the fourth cycle of 223RaCl2. The skeletal tumor burden-expressed as the total lesion fluoride uptake above a maximum standardized uptake value of 10 (TLF10)-was calculated for the baseline and the interim studies. The percent change in TLF10 between the baseline and interim studies (%TFL10) was calculated as follows: %TFL10 = interim TLF10 - baseline TLF10 / baseline TLF10. End points were overall survival, progression-free survival, and skeletal-related events. Results: The mean age of the patients was 72.4 ± 10.2 years (range, 43.3-88.8 years). The %TLF10 was not able to predict overall survival (p = 0.6320; hazard ratio [HR] = 0.753; 95% confidence interval [CI]: 0.236-2.401), progression-free survival (p = 0.5908; HR = 1.248; 95% CI: 0.557-2.797) nor time to a bone event (p = 0.5114; HR = 1.588; 95% CI: 0.399-6.312). Conclusion: The skeletal tumor burden on an interim 18F-fluoride PET/CT, performed after three cycles of 223RaCl2, is not able to predict overall survival, progression-free survival, or time to bone event, and should not be performed to monitor response at this time.

摘要 目的：明确在接受3个周期氯化镭-223（radium-223 dichloride，223RaCl2）治疗后实施的中期18F-氟化钠（18F-fluoride）正电子发射断层显像/计算机断层扫描（positron-emission tomography/computed tomography，PET/CT）检查，能否识别出对该治疗无应答的患者。材料与方法：本研究回顾性分析34例经组织学确诊的骨转移性去势抵抗性前列腺癌患者，所有受试者均接受氯化镭-223治疗。所有患者均完成基线及中期18F-氟化钠PET/CT检查，中期检查于第4个周期氯化镭-223治疗前即刻完成。分别针对基线与中期检查结果计算骨骼肿瘤负荷——以最大标准化摄取值（standardized uptake value，SUV）大于10的总病灶氟摄取量（TLF10）表示。计算基线与中期检查间TLF10的变化百分比（%TLF10），计算公式为：%TLF10 =（中期TLF10 - 基线TLF10）/基线TLF10。本研究的终点指标为总生存期、无进展生存期及骨骼相关事件发生时间。结果：患者的平均年龄为72.4±10.2岁（范围：43.3~88.8岁）。%TLF10无法预测总生存期（p=0.6320；风险比[hazard ratio，HR]=0.753；95%置信区间[confidence interval，CI]：0.236~2.401）、无进展生存期（p=0.5908；HR=1.248；95%CI：0.557~2.797）及骨事件发生时间（p=0.5114；HR=1.588；95%CI：0.399~6.312）。结论：在接受3个周期氯化镭-223治疗后实施的中期18F-氟化钠PET/CT检查所测得的骨骼肿瘤负荷，无法预测总生存期、无进展生存期或骨事件发生时间，因此现阶段不应将该检查用于治疗应答监测。