Delayed <sup>18</sup>F-FDG PET/CT Appearance of Urachal Adenocarcinomas

Xu, Lian; Shi, Yiping; Wang, Yining; Zhou, Xiang; Huang, Gan; Chen, Ruohua; Liu, Jianjun

doi:https://doi.org/10.1155/2020/3216179

Contrast Media & Molecular Imaging

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Abstract Introduction Methods Results Discussion Conclusions Abbreviations Data Availability Ethical Approval Conflicts of Interest Authors’ Contributions Acknowledgments References Copyright Related Articles

Research Article | Open Access

Volume 2020 | Article ID 3216179 | https://doi.org/10.1155/2020/3216179

Delayed ¹⁸F-FDG PET/CT Appearance of Urachal Adenocarcinomas

Lian Xu,¹Yiping Shi,¹Yining Wang,¹Xiang Zhou,¹Gan Huang,¹Ruohua Chen,¹and Jianjun Liu¹

Academic Editor: Barbara Salvatore

Received26 Apr 2020

Revised05 Jul 2020

Accepted28 Aug 2020

Published14 Sept 2020

Abstract

Background. Urachal carcinoma is a rare urological malignancy. Use of ¹⁸F-FDG PET/CT in urological oncology has developed slowly because of the urinary elimination of ¹⁸F-FDG. We investigated whether delayed postdiuretic ¹⁸F-FDG PET/CT could be used for diagnosing urachal carcinoma. Methods. This retrospective study included 6 patients who underwent delayed postdiuretic ¹⁸F-FDG PET/CT for the evaluation of urachal carcinoma. The delayed postdiuretic PET/CT parameters and clinical characteristics of urachal carcinoma were investigated. Results. There was no significant difference in the SUVmax between the primary tumors and the urine in the bladder before delayed diuresis (25.4 ± 19.5 vs. 42.9 ± 31.1, ). However, the SUVmax of the primary tumors was significantly higher than the SUVmax of urine after delayed diuresis (25.4 ± 19.5 vs. 3.5 ± 1.6, ). Diuretic ¹⁸F-FDG PET/CT was positive in all patients when compared with normal liver tissues or urine after delayed diuresis. The SUVmax, TLR, and TUR of the primary tumors were 25.4 (range: 7.2–58.9), 7.0 (range: 1.8–14.7), and 6.8 (range: 3.8–11.3), respectively. Delayed postdiuretic ¹⁸F-FDG PET/CT had a negative predictive value of 100% (5/5) for predicting lymph node metastasis. One patient received chemotherapy after radical resection of urachal carcinoma because ¹⁸F-FDG PET/CT found lung metastases, and one patient only received chemotherapy because PET/CT found peritoneal and skeletal metastases. Conclusions. Delayed postdiuretic ¹⁸F-FDG PET/CT is a useful tool for the preoperative evaluation of urachal carcinoma. ¹⁸F-FDG PET/CT may improve clinical decision making and management of urachal carcinomas.

1. Introduction

Urachal carcinoma is a rare urological malignancy accounting for only 0.34% of all bladder neoplasms, which extends from the bladder dome to the umbilicus [1, 2]. The most common histologic type of urachal carcinoma is adenocarcinomas. Computed tomography and magnetic resonance imaging are the commonly used imaging modalities for the diagnosis of urachal carcinoma [2, 3]. ¹⁸F^-fluorodeoxyglucose (FDG) positron emission tomography (PET) has become a useful modality in cancer evaluation based on hypermetabolism observed in malignant cells [4]. However, use of ¹⁸F-FDG PET/CT, specifically in urological oncology, has developed relatively slowly because the radiotracer is excreted into the urine and bladder, making structures and original tumors difficult to see against the tracer background [5, 6]. It is encouraging to note that ¹⁸F-FDG PET/CT has been used in the diagnosis of bladder cancer through delayed postdiuretic imaging and has exhibited high sensitivity and accuracy in our recent studies [7, 8]. However, because of the rarity of urachal carcinoma, the ¹⁸F-FDG PET/CT literature consists only of case reports [9].

In this study, we describe the delayed ¹⁸F-FDG PET/CT findings in urachal adenocarcinomas, which, to our knowledge, is the first series to assess the diagnostic value of delayed ¹⁸F-FDG PET/CT for urachal carcinomas.

2. Methods

2.1. Patients

We retrospectively reviewed all available clinicopathological data for 6 patients with urachal carcinoma who were examined by delayed postdiuretic ¹⁸F-FDG PET/CT and, subsequently, histologically diagnosed by radical resection of urachal carcinoma (n = 5) or biopsy (n = 1) at the Shanghai Jiaotong University-affiliated Ren Ji Hospital from January 2017 to July 2019. Among the 6 patients, 5 patients were treated with radical resection of urachal carcinoma; the remaining one patient was treated with chemotherapy. The study was approved by the institutional review board of the Shanghai Jiaotong University-affiliated Ren Ji Hospital and was in accordance with the 2013 revision of the Declaration of Helsinki. The need for informed consent was waived in this study.

2.2. Delayed Postdiuretic ¹⁸F-FDG PET/CT Imaging

Blood glucose levels were measured and found to be less than 140 mg/dL at the time the ¹⁸F-FDG was administered. All patients received an intravenous 3.7 MBq/kg injection of ¹⁸F-FDG after fasting for at least 6 h and resting for 1 h. ¹⁸F-FDG PET/CT scanning from the groin to the skull base was performed using a whole-body scanner (Biograph mCT; Siemens, Erlangen, Germany) (early PET/CT imaging). After early PET/CT imaging, delayed postdiuretic PET/CT imaging was performed after 120 min of early PET/CT imaging. Patients received 20 mg of furosemide by the oral route and an extra oral intake of at least 500 mL water. Patients were asked to void frequently to reduce the urine physiological uptake of the radiotracer ¹⁸F-FDG. Delayed imaging covered a range of one or two bed positions centered at the location of the bladder. PET images were attenuation-corrected and anatomically correlated with low-dose CT images.

For quantitative analysis, irregular regions of interest were placed over the most intense area of ¹⁸F-FDG uptake on delayed postdiuretic PET/CT imaging. The SUVmax was calculated as (maximum pixel value with the decay-corrected region-of-interest activity [MBq/mL])/(injected dose [MBq]/body weight [kg]). The PET/CT images were evaluated by two experienced nuclear medicine physicians. The TLR was calculated as the SUVmax of primary tumors/SUVmax of the liver. The TUR was calculated as the SUVmax of primary tumors/SUVmax of urine (delay).

2.3. Statistical Analysis

The data are presented as mean ± SD. Statistically significant differences between groups were compared using the Mann–Whitney U-test. was considered statistically significant. Statistical analyses were performed using SPSS, version 13.0 (SPSS Inc.).

3. Results

3.1. Patient Characteristics

The patient characteristics and delayed ¹⁸F-FDG PET/CT finding are listed in Table 1. There were 3 males and 3 females with an average age of 48.7 (range 35–71 years). The tumor size averaged 4.3 cm in the largest cross-sectional diameter (range 2.8–7.8 cm). Five cases appeared as solid lesions and one case appeared as mixed cystic-solid lesion. Four cases appeared as a round-like nodule or mass and two cases appeared as irregular lumps. All were adenocarcinomas. Calcifications were radiologically visible in one case. One case (Case 2) had distant metastasis in the peritoneal and bone. In our series, 5 patients (83.3%) presented with hematuria as the first clinical sign, and 1 patient (16.7%) presented with painful pelvic mass as the first clinical sign.

3.2. PET Appearance

The mean SUVmax of urine in the bladder of the early image was 42.9 (range 13.5–91.6), so the SUVmax of lesion cannot be easily detected due to urine interference, especially for the intraluminal portion. On the image of 18F-FDG PET/CT in the delayed phase, the bladder is distended and the SUVmax of urine was very low (mean, 3.5; range 1.8–5.2). So, the lesion can be easily visualized by axial CT and PET, particularly the intraluminal portion of the mass. Diuretic 18F-FDG PET/CT was positive in all patients when compared with normal liver tissues or urine after delayed diuresis. The SUVmax of primary tumors before diuresis was 23.6 (range 6.8–60.1).The SUVmax after diuresis, TLR, and TUR of the primary tumors were 25.4 (range 7.2–58.9), 7.0 (range 1.8–14.7), and 6.8 (range 3.8–11.3), respectively. The SUVmax of the primary tumors was significantly higher than the SUVmax of urine after delayed diuresis (25.4 ± 19.5 vs. 3.5 ± 1.6, ). However, there was no significant difference in the SUVmax between the primary tumors and the urine before delayed diuresis (25.4 ± 19.5 vs 42.9 ± 31.1, ). Representative images of a patient (Case 3) with urachal carcinoma who underwent ¹⁸F-FDG PET/CT scanning (early PET/CT imaging) and delayed postdiuretic PET/CT scanning are shown in Figure 1.

(a)

(b)

Figure 1

(a) Images of a 44-year-old man with urachal carcinoma (Case 3). On the ¹⁸F-FDG PET/CT images, axial CT shows that the space-occupying lesion was located in the bladder dome. However, the ¹⁸F-FDG uptake of the lesion cannot be easily detected because of urine interference in the early image (early). (b) On the image of ¹⁸F-FDG PET/CT in the delayed phase, the ureter is distended and the lesion can be easily visualized by axial CT and PET (SUVmax, 58.9) (delay) as the ¹⁸F-FDG uptake of urine in the bladder was very low (SUVmax, 5.2). The patient underwent radical resection of urachal carcinoma, and moderately differentiated adenocarcinoma was confirmed by histopathology.

Of the 6 patients, 2 patients underwent ultrasound examination, 1 patient underwent computed tomography, and 3 patients underwent MRI. Though they all found the primary tumors, they did not find any metastatic lesion. Of the 6 patients, 4 patients underwent radical resection of urachal carcinoma because PET/CT found no lymph node and distant metastasis. Postoperative pathology further confirmed the ¹⁸F-FDG PET/CT results. One patient (Case 1) received chemotherapy after radical resection of urachal carcinoma because ¹⁸F-FDG PET/CT found lung metastases, though ¹⁸F-FDG PET/CT and postoperative pathology both found no lymph node metastasis. Thus, 18F-FDG PET/CT had a negative predictive value of 100% (5/5) for predicting lymph node metastasis. One patient (Case 2) only received chemotherapy because PET/CT found peritoneal and skeletal metastases.

4. Discussion

¹⁸F-FDG PET/CT has been widely used for diagnosis of various malignant tumors [10–12]. Unfortunately, ¹⁸F-FDG is not an ideal radiotracer for use in urology because of its urinary elimination [13]. In this study, the potential of delayed postdiuretic ¹⁸F-FDG PET/CT for diagnosing urachal carcinoma was analyzed. To the best of our knowledge, this was the first study to assess the diagnostic value of delayed ¹⁸F-FDG PET/CT in urachal carcinomas.

Though Yang et al. reported a case of urachal carcinoma detected by ¹⁸F-FDG PET/CT, it consists of only one case and delayed postdiuretic ¹⁸F-FDG PET/CT was untaken [9]. So, the SUVmax of urachal carcinoma cannot be easily detected due to urine interference in this case. Several investigators have considered ¹⁸F-FDG PET/CT of no utility in the detection of localized urological malignancies and lymph nodes [14]. The limitation of ¹⁸F-FDG PET/CT has been attributed to the urinary excretion of ¹⁸F-FDG. The pooled activity in the urinary system makes the evaluation of urinary lesions difficult. Catheterization has been proposed to reduce bladder spillover for the evaluation of the pelvic region in several studies. In addition to catheterization, our previous studies showed that washing out the excreted ¹⁸F-FDG could also overcome this limitation in bladder cancer [7, 8]. Delayed postdiuretic ¹⁸F-FDG PET/CT exhibited high sensitivity and accuracy for diagnosing bladder cancer in these studies [7, 8]. In this study, we showed that the lesion of urachal carcinomas can be easily visualized by delayed postdiuretic ¹⁸F-FDG PET/CT and the lesion was positive in all patients when compared with normal liver tissues or urine after delayed diuresis.

CT and MRI have been used to assess the local extent of urachal carcinomas and the presence of pelvic and visceral metastases [15]. However, they have limitations because they can detect only lymph nodes and distant metastasis that are quite enlarged. CT fails to detect lymph node involvement in up to 40–70% of patients with lymph node metastases [16]. ¹⁸F-FDG PET/CT was, however, more sensitive than conventional CT scan in detecting lymph node metastases based on hypermetabolism of lymph node involvement [17]. In this study, 2 patients underwent ultrasound examination, 1 patient underwent computed tomography, and 3 patients underwent MRI. Though they all found the primary tumors, they did not find any metastatic lesion. ¹⁸F-FDG PET/CT found no lymph node metastasis in 5 cases, and postoperative pathology further confirmed the accuracy. Thus, delayed postdiuretic 18F-FDG PET/CT had a negative predictive value of 100% (5/5) for predicting lymph node metastasis in our study. In one patient, radical resection of urachal carcinoma was not performed because PET/CT found peritoneal and skeletal metastases. Thus, delayed postdiuretic ¹⁸F-FDG PET/CT have the potential to improve clinical decision making and management of urachal carcinomas.

Our study was, in part, limited by its retrospective design and small sample size. Although delayed postdiuretic ¹⁸F-FDG PET/CT may have a good diagnostic performance for urachal carcinoma, further large and prospective studies were needed to confirm our results.

5. Conclusions

Our results were the first to show the diagnostic value of delayed postdiuretic ¹⁸F-FDG PET/CT in the urachal carcinomas. These results may advance the development of noninvasive strategies to improve clinical decision making and management of urachal carcinomas. Further larger and prospective studies that include more clinical samples are needed to confirm the value and efficacy of delayed postdiuretic ¹⁸F-FDG PET/CT in urachal carcinomas.

Abbreviations

¹⁸F-FDG PET:	¹⁸F^-fluorodeoxyglucose positron emission tomography
SUVmax:	The maximum of standardized uptake value.

Data Availability

The data used to support the findings of this study are available from the corresponding author upon request.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the principles of the institutional review board of Shanghai Jiao Tong University-affiliated Ren ji Hospital and the 1975 Declaration of Helsinki, as revised in 2013. This article does not contain any studies with animals performed by any of the authors.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Authors’ Contributions

LJJ and CRH designed the experiments. XL, WYN, ZX, and HG performed data collection and the statistical analysis. CRH and SYP wrote the manuscript and replied to the reviews. Lian Xu, Yiping Shi, and Yining Wang contributed equally to this work. All authors approved the final draft of this manuscript.

Acknowledgments

This work was supported by grants from the National Natural Science Foundation of China (nos. 81701724, 81771858, 81830052, 81530053, 81602415, 81571710, 81771861, 81601520, 81601536, and 81572719) and Innovative research team of high-level local universities in Shanghai.

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Copyright © 2020 Lian Xu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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