Abstract

Purpose

⁶⁸Ga-PSMA-11-PET/CT is increasingly used in early-stage biochemical recurrence of prostate cancer to detect potential lesions for an individualized radiotherapy concept. However, subtle findings especially concerning small local recurrences can still be challenging to interpret and are prone to variability between different readers. Thus, we analyzed interobserver variability, detection rate, and lesion patterns systematically in a homogeneous patient population with low-level biochemical recurrence.

Methods

We analyzed ⁶⁸Ga-PSMA-11-PET/CTs in 116 patients with status post-prostatectomy and PSA levels up to 0.6 ng/ml. None of them received ADT or radiotherapy beforehand. Images were interpreted and blinded by two nuclear medicine physicians (R1 and R2). Findings were rated using a 5-point scale concerning local recurrence, lymph nodes, bone lesions, and other findings (1: definitely benign, 2: probably benign, 3: equivocal, 4: probably malignant, 5: definitely malignant). In findings with substantial discrepancies of 2 or more categories and/or potentially leading to differences in further patient management, a consensus reading was done with a third reader (R3). Interobserver agreement was measured by Cohens Kappa analysis after sub-categorizing our classification system to benign (1 + 2), equivocal (3), and malignant (4 + 5). Time course of PSA levels after salvage treatment of patients rated as positive (4 + 5) was analyzed.

Results

The overall detection rate (categories 4 and 5) was 50% (R1/R2, 49%/51%) and in the PSA subgroups 0–0.2 ng/ml, 0.21–0.3 ng/ml, and 0.31–0.6 ng/ml 24%/27%, 57%/57%, and 65%/68%, respectively. Local recurrence was the most common lesion manifestation followed by lymphatic and bone metastases. The overall agreement in the Cohens Kappa analysis was 0.74 between R1 and R2. For local, lymphatic, and bone sites, the agreement was 0.76, 0.73, and 0.58, respectively. PSA levels of PSMA PET/CT-positive patients after salvage treatment decreased in 75% (27/36) and increased in 25% (9/36). A decrease of PSA, although more frequent in patients with imaging suggesting only local tumor recurrence (86%, 18/21), was also observed in 67% (10/15) of patients with findings of metastatic disease.

Conclusions

In a highly homogeneous group of prostate cancer patients with early-stage biochemical recurrence after radical prostatectomy, we could show that ⁶⁸Ga-PSMA-11-PET/CT has a good detection rate of 50% which is in accordance with literature, with clinically relevant findings even in patients with PSA < 0.21 ng/ml. The interobserver variability is low, particularly concerning assessment of local recurrences and lymph nodes. Therefore, PSMA-PET/CT is a robust diagnostic modality in this patient group for therapy planning.

中文翻译：

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68Ga-PSMA-11-PET/CT 在前列腺癌根治术后早期生化复发中的观察者间变异性、检出率和病变模式。

 抽象的

 目的

⁶⁸ Ga-PSMA-11-PET/CT 越来越多地用于前列腺癌的早期生化复发，以检测个体化放射治疗概念的潜在病变。然而，微妙的发现，特别是关于小局部复发的微妙发现仍然难以解释，并且不同读者之间容易出现差异。因此，我们系统地分析了具有低水平生化复发的同质患者群体中观察者间的变异性、检出率和病变模式。

 方法

我们分析了 116 名前列腺切除术后状态且 PSA 水平高达 0.6 ng/ml 的患者的^{68 个}Ga-PSMA-11-PET/CT。他们事先均未接受 ADT 或放射治疗。图像由两名核医学医师（R1 和 R2）进行解读和盲法。使用关于局部复发、淋巴结、骨病变和其他发现的 5 级量表对结果进行评级（1：绝对良性，2：可能良性，3：模棱两可，4：可能恶性，5：绝对恶性）。对于 2 个或多个类别存在重大差异和/或可能导致进一步患者管理差异的结果，由第三位读者 (R3) 进行共识解读。将我们的分类系统细分为良性 (1 + 2)、模棱两可 (3) 和恶性 (4 + 5) 后，通过 Cohens Kappa 分析测量观察者间的一致性。对评定为阳性（4+5）的患者进行挽救治疗后 PSA 水平的时间进程进行了分析。

 结果

总体检出率（第 4 类和第 5 类）为 50%（R1/R2，49%/51%），PSA 亚组为 0-0.2 ng/ml、0.21-0.3 ng/ml 和 0.31-0.6 ng/ml分别为 24%/27%、57%/57% 和 65%/68%。局部复发是最常见的病变表现，其次是淋巴转移和骨转移。 R1 和 R2 之间 Cohens Kappa 分析的总体一致性为 0.74。对于局部、淋巴和骨骼部位，一致性分别为 0.76、0.73 和 0.58。挽救治疗后，PSMA PET/CT 阳性患者的 PSA 水平下降了 75% (27/36)，上升了 25% (9/36)。 PSA 下降虽然在影像学提示仅局部肿瘤复发的患者中更为常见（86%，18/21），但在 67%（10/15）发现转移性疾病的患者中也观察到了 PSA 下降。

 结论

在一组高度同质的前列腺癌根治术后早期生化复发的患者中，我们可以表明⁶⁸ Ga-PSMA-11-PET/CT 具有 50% 的良好检出率，这与文献一致，临床上即使在 PSA < 0.21 ng/ml 的患者中也有相关发现。观察者间的变异性较低，特别是在局部复发和淋巴结的评估方面。因此，PSMA-PET/CT 是该患者组治疗规划的一种强有力的诊断方式。