本研究的目的是分析转移性去势抵抗性前列腺癌患者在治疗周期中骨与淋巴转移中吸收的177Lu-PSMA剂量，并将这些数据与治疗效果相关联。此外，还评估了术前的前列腺特异性膜抗原（PSMA）PET/CT在预测疗效的能力。方法：本研究包括30例转移性去势抵抗性前列腺癌患者，每个患者均接受至少3个177Lu-PSMA疗程。基线和第三个疗程后6周的前列腺特异性抗原（PSA）值用于将患者划分为反应良好组（PSA下降≥ 50%）或非反应组（PSA水平不变或增加）。使用量化的SPECT/CT图像在注射177Lu-PSMA后的24、48和168小时内获取。使用剂量学软件计算瘤灶的吸收剂量。从术前PET/CT扫描中，确定不同SUV值的肿瘤与肾脏摄取比。结果：无论患者的反应如何，肾脏每个周期平均接受0.55±0.20 Gy/GBq的剂量。在第一个疗程中，淋巴结病灶在反应良好组中平均接受3.73±1.65 Gy/GBq的剂量，在非反应组中为1.86±1.25 Gy/GBq（P < 0.01）。对于骨病灶，相应的平均剂量为3.47±2.00 Gy/GBq和1.48±0.95 Gy/GBq（P < 0.01）。比较连续的疗程后发现，淋巴结和骨病变的平均剂量相较于第一个周期分别减少了27%和33%。根据术前PET/CT扫描结果可以得出结论，在反应良好组与非反应组之间，淋巴结和骨病变摄取率与肾脏摄取率的比例存在显著差异（P < 0.01）。结论：反应良好组的淋巴结和骨病灶剂量明显较高。在第一个疗程中达到了淋巴和骨病变的最高剂量，尽管治疗活性不变，在第二个疗程之后剂量有所减少。通过术前PSMA PET/CT扫描得到的肿瘤摄取率与肾脏摄取率的比例可能有助于预测治疗效果。© 2023年核医学与分子影像学会。

The aim of this study was to analyze the absorbed dose of 177Lu-PSMA in osseous versus lymphatic metastases in patients with metastatic castration-resistant prostate cancer across therapy cycles and to relate those data to therapeutic success. In addition, pretherapeutic prostate-specific membrane antigen (PSMA) PET/CT was evaluated for its ability to predict response behavior. Methods: The study comprised 30 patients with metastatic castration-resistant prostate cancer, each receiving at least 3 cycles of 177Lu-PSMA therapy. Prostate-specific antigen (PSA) values between baseline and 6 wk after the third therapy cycle were used to classify the patients as responders (PSA decline ≥ 50%) or nonresponders (unchanged or increasing PSA level). Quantitative SPECT/CT images were acquired 24, 48, and 168 h after application of 177Lu-PSMA. The absorbed dose for tumor lesions was calculated with dosimetry software. From the pretherapeutic PET/CT scan, the tumor-to-kidney uptake ratio was determined for different SUVs. Results: Regardless of patient response, the kidneys received a mean dose of 0.55 ± 0.20 Gy/GBq per cycle. In the first therapy cycle, the lymph node lesions received a mean dose of 3.73 ± 1.65 Gy/GBq in responders and 1.86 ± 1.25 Gy/GBq in nonresponders (P < 0.01). For bone lesions, the respective mean doses were 3.47 ± 2.00 Gy/GBq and 1.48 ± 0.95 Gy/GBq (P < 0.01). When successive therapy cycles were compared, the mean dose was found to have been reduced from the first to the second cycle by 27% for lymph nodes and by 33% for bone lesions. A significant difference (P < 0.01) in the ratio of lymph node and bone lesion uptake to kidney uptake between responders and nonresponders could be deduced from the pretherapeutic PET/CT scan. Conclusion: Significantly higher doses were achieved for lymph node and bone lesions in responders. The highest absorbed dose, for both lymphatic and osseous lesions, was achieved in the first cycle, decreasing in the second therapy cycle thereafter despite unchanged therapy activities. It may be possible to estimate the response to therapy from the ratio of tumor uptake to kidney uptake obtained from the pretherapeutic PSMA PET/CT scans.© 2023 by the Society of Nuclear Medicine and Molecular Imaging.