Pelvic Lymph Node Staging by Combined 18F-FDG-PET/CT Imaging in Bladder Cancer Prior to Radical Cystectomy

Management of patients with muscle-invasive bladder cancer with clinical evidence of pelvic lymph node metastases

Identification of clinically positive pelvic lymph node metastases (cN+) in patients with muscle-invasive bladder cancer is currently challenging, as the diagnostic accuracy of available imaging modalities is limited. Conventional CT is still considered the gold-standard approach to diagnose lymph node metastases in these patients. The development of innovative diagnostic methods including radiomics, artificial intelligence-based models and molecular biomarkers might offer new perspectives for the diagnosis of cN+ disease. With regard to the treatment of these patients, multimodal strategies are likely to provide the best oncological outcomes, especially using induction chemotherapy followed by radical cystectomy and pelvic lymph node dissection in responders to chemotherapy. Additionally, the use of adjuvant nivolumab has been shown to decrease the risk of recurrence in patients who still harbour ypT2-T4a and/or ypN+ disease after surgery. Alternatively, the use of avelumab maintenance therapy can be offered to patients with unresectable cN+ tumours who have at least stable disease after induction chemotherapy alone. Lastly, patients with cN+ tumours who are not responding to induction chemotherapy are potential candidates for receiving second-line treatment with pembrolizumab.

FDG-PET/CT for lymph node staging prior to radical cystectomy

BACKGROUND

¹⁸F-Fluorodeoxyglucose positron emission combined with computed tomography (FDG-PET/CT) has been proposed to improve preoperative staging in patients with bladder cancer subjected to radical cystectomy (RC).

OBJECTIVE

Our aim was to assess the accuracy of FDG-PET/CT for lymph node staging ascertained at the multidisciplinary tumour board compared to lymph node status in the surgical lymphadenectomy specimen obtained at RC, and to explore potential factors associated with false-positive FDG-PET/CT results.

DESIGN, SETTING AND PARTICIPANTS

Consecutive patients with bladder cancer undergoing RC with extended lymph node dissection between 2011 and 2019 without preoperative chemotherapy in a tertial referral cystectomy unit were included in the study.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSES

Sensitivity, specificity, positive and negative predictive values and likelihood ratios were calculated. Potential factors investigated for association with false-positive FDG-PET/CT were; bacteriuria within four weeks prior to FDG-PET/CT, Bacillus Calmette-Guerin (BCG) treatment within 12 months prior to FDG-PET/CT and transurethral resection of bladder tumour (TURB) within four weeks prior to FDG-PET/CT.

RESULTS

Among 157 patients included for analysis, 44 (28%) were clinically node positive according to FDG-PET/CT. The sensitivity and specificity for detection of lymph node metastasis were 50% and 84%, respectively, and the corresponding positive predictive and negative predictive values were 61% and 76%. Positive and negative likelihood ratios were 3.0 and 0.6, respectively. No association was found between bacteriuria, previous BCG treatment or TURB within 28 days and false-positive FDG-PET/CT results.

CONCLUSIONS

Preoperative FDG-PET/CT prior to RC had a clinically meaningful high specificity (84%) but lower sensitivity (50%) for detection of lymph node metastases compared to lymph node status in an extended pelvic lymphadenectomy template. We could not identify any factors associated with false-positive FDG-PET/CT outcomes.

Assessing the Performance of 18F-FDG PET/CT in Bladder Cancer: A Narrative Review of Current Evidence

INTRODUCTION

Lymph node (LN) involvement is a crucial determinant of prognosis for patients with bladder cancer, and an accurate staging is of utmost importance to better identify timely and appropriate therapeutic strategies. To improve the accuracy of LN detection, as an alternative to traditional methods such as CT or MRI, 18F-FDG PET/CT has been increasingly used. 18F-FDG PET/CT is also used in post-treatment restaging after neoadjuvant chemotherapy. The aim of this narrative literature review is to provide an overview of the current evidence on the use of 18F-FDG PET/CT in the diagnosis, staging, and restaging of bladder cancer, with a particular focus on its sensitivity and specificity for the detection of LN metastasis. We aim to provide clinicians with a better understanding of 18F-FDG PET/CT's potential benefits and limitations in clinical practice.

MATERIALS AND METHODS

We designed a narrative review starting from a wide search in the PubMed/MEDLINE and Embase databases, selecting full-text English articles that have examined the sensibility and specificity of PET/CT for nodal staging or restaging after neoadjuvant therapy in patients with bladder cancer. The extracted data were analyzed and synthesized using a narrative synthesis approach. The results are presented in a tabular format, with a summary of the main findings of each study.

RESULTS

Twenty-three studies met the inclusion criteria: fourteen studies evaluated 18F-FDG PET/CT for nodal staging, six studies examined its accuracy for restaging after neoadjuvant therapy, and three studies evaluated both applications. To date, the use of F-18 FDG PET/TC for detection of LN metastasis in bladder cancer is controversial and uncertain: some studies showed low accuracy rates, but over the years other studies have reported evidence of high sensitivity and specificity.

CONCLUSIONS

18F-FDG PET/CT provides important incremental staging and restaging information that can potentially influence clinical management in MIBC patients. Standardization and development of a scoring system are necessary for its wider adoption. Well-designed randomized controlled trials in larger populations are necessary to provide consistent recommendations and consolidate the role of 18F-FDG PET/CT in the management of bladder cancer patients.

The Implementation of FDG PET/CT for Staging Bladder Cancer: Changes in the Detection and Characteristics of Occult Nodal Metastases at Upfront Radical Cystectomy?

Occult lymph node (LN)-metastases are frequently found after upfront radical cystectomy (uRC) for bladder cancer (BC). We evaluated whether the implementation of 18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG PET/CT) influenced nodal staging at uRC. All consecutive BC patients who underwent uRC with bilateral pelvic lymph node dissection (PLND) were identified and divided into two cohorts: cohort A consisted of patients staged with FDG PET/CT and contrast-enhanced CT (CE-CT) (2016-2021); cohort B consisted of patients staged with CE-CT only (2006-2011). The diagnostic performance of FDG PET/CT was assessed and compared with that of CE-CT. Thereafter, we calculated the occult LN metastases proportions for both cohorts. In total, 523 patients were identified (cohort A n = 237, and cohort B n = 286). Sensitivity, specificity, PPV and NPV of FDG PET/CT for detecting LN metastases were 23%, 92%, 42%, and 83%, respectively, versus 15%, 93%, 33%, 81%, respectively, for CE-CT. Occult LN metastases were found in 17% of cohort A (95% confidence interval (CI) 12.2-22.8) and 22% of cohort B (95% CI 16.9-27.1). The median size of LN metastases was 4 mm in cohort A versus 13 mm in cohort B. After introduction of FDG PET/CT, fewer and smaller occult LN metastases were present after uRC. Nevertheless, up to one-fifth of occult (micro-)metastases were still missed.

Pelvic lymph node dissection in prostate and bladder cancers

Prostate cancer and bladder cancer accounts for approximately 13.5% and 3% of all male cancers and all newly diagnosed cancers (regardless sex), respectively. Thus, these cancers represent a major health and economic burden globally. The knowledge of lymph node status is an integral part of the management of any solid tumor. In the urological field, pelvic lymph node dissection (PLND) is of paramount importance in the diagnosis, management, and prognosis of prostate and bladder cancers. However, PLND may be associated with several comorbidities. In this narrative review, the most recent updates concerning the patterns and incidence of lymph node metastasis, the role of different imaging studies and nomograms in determining patients' eligibility for PLND, and the anatomical templates of PLND in urologic patients with bladder or prostate cancer will be discussed.

Management of Bladder Cancer Patients with Clinical Evidence of Lymph Node Invasion (cN+)

The purpose of this review is to present the current knowledge about the diagnostic and treatment options for bladder cancer (BCa) patients with clinically positive lymph nodes (cN+). This review shows compaction of CT and MRI performance in preoperative prediction of lymph node invasion (LNI) in BCa patients, along with other diagnostic methods. Most scientific societies do not distinguish cN+ patients in their guidelines; recommendations concern muscle-invasive bladder cancer (MIBC) and differ between associations. The curative treatment that provides the best long-term survival in cN+ patients is a multimodal approach, with a combination of neoadjuvant chemotherapy (NAC) and radical cystectomy (RC) with extended pelvic lymph node dissection (ePLND). The role of adjuvant chemotherapy (AC) remains uncertain; however, emerging evidence indicates comparable outcomes to NAC. Therefore, in cN+ patients who have not received NAC, AC should be implemented. The response to ChT is a crucial prognostic factor for cN+ patients. Recent studies demonstrated the growing importance of immunotherapy, especially in ChT-ineligible patients. Moreover, immunotherapy can be suitable as adjuvant therapy in selected cases. In cN+ patients, the extended template of PLND should be utilized, with the total resected node count being less important than the template. This review is intended to draw special attention to cN+ BCa patients, as the oncological outcomes are significantly worse for this group.

Value of Clinical Information on Radiology Reports in Oncological Imaging

Radiological reporting errors have a direct negative impact on patient treatment. The purpose of this study was to investigate the contribution of clinical information (CI) in radiological reporting of oncological imaging and the dependence on the radiologists’ experience level (EL). Sixty-four patients with several types of carcinomas and twenty patients without tumors were enrolled. Computed tomography datasets acquired in primary or follow-up staging were independently analyzed by three radiologists (R) with different EL (R1: 15 years; R2: 10 years, R3: 1 year). Reading was initially performed without and 3 months later with CI. Overall, diagnostic accuracy and sensitivity for primary tumor detection increased significantly when receiving CI from 77% to 87%; p = 0.01 and 73% to 83%; p = 0.01, respectively. All radiologists benefitted from CI; R1: 85% vs. 92%, p = 0.15; R2: 77% vs. 83%, p = 0.33; R3: 70% vs. 86%, p = 0.02. Overall, diagnostic accuracy and sensitivity for detecting lymphogenous metastases increased from 80% to 85% (p = 0.13) and 42% to 56% (p = 0.13), for detection of hematogenous metastases from 85% to 86% (p = 0.61) and 46% to 60% (p = 0.15). Specificity remained stable (>90%). Thus, CI in oncological imaging seems to be essential for correct radiological reporting, especially for residents, and should be available for the radiologist whenever possible.

Feasibility of [68Ga]Ga-FAPI-46 PET/CT for detection of nodal and hematogenous spread in high-grade urothelial carcinoma

Background

[⁶⁸Ga]Ga-FAPI-46 is a novel positron emission tomography (PET) ligand that targets fibroblast activation protein (FAP) expression as FAP inhibitor (FAPI) and could already show promising results in several tumor entities. It could be demonstrated that an increased FAP expression correlates with tumor aggressivity in urothelial carcinoma (UC). Given the limited value of [¹⁸F]FDG in UC, [⁶⁸Ga]Ga-FAPI-46 could add diagnostic information in staging and response assessment in UC. We present the first data of [⁶⁸Ga]Ga-FAPI-46 PET imaging in a pilot cohort of UC patients evaluating uptake characteristics in metastases and primary tumors.

Methods

Fifteen patients with UC prior to or after local treatment underwent [⁶⁸Ga]Ga-FAPI-46 PET/CT imaging for detection of metastatic spread. We compared the biodistribution in non-affected organs and tumor uptake of UC lesions by standard uptake value measurements (SUV_mean and SUV_max). Additionally, metastatic sites on PET were compared to its morphological correlate on contrast-enhanced computed tomography (CT).

Results

Overall, 64 tumor sites were detected on PET and/or CT. The highest uptake intensity was noted at the primary site (SUV_max 20.8 (range, 8.1–27.8)) followed by lymph node metastases (SUV_max 10.6 (range, 4.7–29.1)).

In 4/15 (26.7%) patients there were [⁶⁸Ga]Ga-FAPI-46-positive lesions that were missed on standard routine CT imaging. On the other hand, 2/15 patients had suspicious prominent bipulmonary nodules as well as pelvic lymph nodes previously rated as suspicious for metastatic spread on CT, but without increased FAPI expression; here histopathology excluded malignancy.

Conclusion

[⁶⁸Ga]Ga-FAPI-46 PET shows distinctly elevated uptake in UC lesions. Therefore, the tracer has potential as a promising new biomarker in metastatic UC patients, as [⁶⁸Ga]Ga-FAPI-46 PET might improve detection of metastatic sites compared to CT alone. These findings highly emphasize larger studies investigating FAPI imaging in UC patients.

The impact of 18F-fluorodeoxyglucose PET/computed tomography on clinical staging in bladder cancer

AIM

To determine the impact of 18F-FDG PET/computed tomography (CT) on clinical staging in bladder cancer with comparison to conventional CT and MRI.

METHODS

A total of 142 patients who underwent 18F-FDG PET/CT imaging with a diagnosis of bladder cancer between 1 June 2019 and 31 December 2020 were screened retrospectively. Seventy patients who underwent diagnostic CT or MRI within 2 months before or after PET/CT were included in the study. The N and M stages determined by CT, MRI and PET/CT according to the eighth version of the TNM staging system were recorded. T-test was used to determine the levels of significant difference, and univariate logistic regression analysis was used to evaluate the impact of the T stage on nodal up-staging.

RESULTS

According to the PET/CT, the N stage increased in 19 patients (27.14%) and decreased in seven patients (10%). Likewise, the M stage increased in 16 patients (22.86%) and decreased in seven patients (10%). The N stage determined by PET/CT was confirmed by pathologic examination in all cases in which the two modalities were inconsistent. In muscle-invasive cases, the rate of increase in the N stage after PET/CT (36.95%) was found to be significantly higher than in that of cases without invasion (8.33%) (P = 0.011). Increasing T stage was associated with an increase in the N stage after PET/CT (odds ratio: 2.33, 95% confidence interval: 1.02-5.28, P = 0.042).

CONCLUSION

18F-FDG PET/CT can potentially change the clinical stage determined by CT and MRI when used for staging in bladder cancer, and can lead to nodal up-staging particularly in cases with muscle-invasive bladder cancer.

PET/CT in Bladder Cancer: An Update

In the urinary tract, bladder cancer is the most common malignancy. It is a heterogenous cancer type with approximately 30% presenting as muscle invasive bladder cancer with a high risk of metastatic spread associated with risk of death from distant metastases. The other 70% of bladder cancer patients present with superficial tumors with tendency of recurrence but in general not life-threatening. Like in other malignancies, accurate and precise staging of bladder cancer is one of the mainstays at the time of diagnosis to select the optimal treatment for each patient. The detection of metastatic spread is of utmost importance for selection of treatment strategy. Hybrid imaging med with FDG PET/CT is widely used in the clinical management of a variety of malignancies. FDG PET/CT is increasingly used for primary staging of muscle invasive bladder cancer and for detection of recurrence after radical cystectomy. Few studies have used FDG PET/CT for response evaluation of neoadjuvant, induction chemotherapy or immunotherapy. Furthermore, small studies have tested non-FDG PET agents with little or no urinary excretions of the tracer. This review provides an update on PET/CT in bladder cancer.

The Role of Molecular Imaging in a Muscle-Invasive Bladder Cancer Patient: A Narrative Review in the Era of Multimodality Treatment

Diagnostic imaging in bladder cancer plays an important role since it is needed from pretreatment staging to follow-up, but a morphological evaluation performed with both CT and MRI showed low sensitivities and specificities in detecting pathologic lymph nodes, due to the occurrence of false positive results. Implementation of functional information provided by PET/CT could be a determinant in the management of patients with muscle-invasive bladder cancer. A focus on the role of ¹⁸F-FDG PET/CT and alternative tracers in patients with muscle-invasive bladder cancer is provided in this analysis in order to outline its potential applications in staging settings and response evaluation after neoadjuvant chemotherapy.

Diagnosis and Staging of Bladder Cancer

Cystoscopic examination remains the gold standard technique for initial diagnosis of bladder cancer (BCa). Despite significant progress in enhanced cystoscopic techniques, blue light cystoscopy and narrow band imaging are the only ones well supported by high-level evidence and, if available, should be used during initial staging of BCa. Multiparametric MRI could be an important imaging tool in local staging of BCa. With ever-expanding targeted therapy and immunotherapy options in both muscle-invasive and non-muscle-invasive BCa, molecular subtyping could become an essential part of initial histologic staging in the near future.

Imaging of Bladder Cancer: Standard Applications and Future Trends

The evolution in imaging has had an increasing role in the diagnosis, staging and follow up of bladder cancer. Conventional cystoscopy is crucial in the diagnosis of bladder cancer. However, a cystoscopic procedure cannot always depict carcinoma in situ (CIS) or differentiate benign from malignant tumors prior to biopsy. This review will discuss the standard application, novel imaging modalities and their additive role in patients with bladder cancer. Staging can be performed with CT, but distinguishing between T1 and T2 BCa (bladder cancer) cannot be assessed. MRI can distinguish muscle-invasive from non-muscle-invasive tumors with accurate local staging. Vesical Imaging-Reporting and Data System (VI-RADS) score is a new diagnostic modality used for the prediction of tumor aggressiveness and therapeutic response. Bone scintigraphy is recommended in patients with muscle-invasive BCa with suspected bony metastases. CT shows low sensitivity for nodal staging; however, PET (Positron Emission Tomography)/CT is superior and highly recommended for restaging and determining therapeutic effect. PET/MRI is a new imaging technique in bladder cancer imaging and its role is promising. Texture analysis has shown significant steps in discriminating low-grade from high-grade bladder cancer. Radiomics could be a reliable method for quantitative assessment of the muscle invasion of bladder cancer.

Role of PET/CT in muscle-invasive bladder cancer

The purpose of this study covered the diagnostic accuracy and usefulness of positron emission tomography/computed tomography (PET/CT) imaging in muscle invasive bladder cancer patients through previously published literature. Through 30 September, 2019, the PubMed database was searched for eligible articles that evaluated PET/CT imaging in bladder cancer patients. In general, FDG PET/CT, the most commonly used PET/CT imaging, does not show good performance for the detection of primary lesions; however, according to the literature it could accurately assess pelvic lymph node (LN) status better than other imaging technologies and it was especially helpful in determining extra-pelvic recurrences. More recently, non-FDG PET/CT imaging, such as C-11 acetate and C-11 choline, has been introduced. Although further research is required, preliminary results show the potential of these techniques to overcome the drawbacks of FDG. This concise study will overview the role of PET/CT when treating muscle-invasive bladder cancer (MIBC).

18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography in muscle-invasive bladder cancer

PURPOSE OF REVIEW

In this narrative review, we assessed the role of F-fluoro-2-deoxy-D-glucose-positron emission tomography/CT (FDG-PET/CT) in preoperative staging and response evaluation of neoadjuvant chemotherapy in muscle-invasive bladder carcinoma (MIBC), and to assess its incremental value to contrast-enhanced (CE)CT and MRI in terms of patient management at initial diagnosis and detection of recurrence.

RECENT FINDINGS

A literature search in PubMed yielded 46 original reports, of which 15 compared FDG-PET/CT with CECT and one with MRI. For primary tumor assessment, FDG-PET/CT proved not accurate enough (13 reports; n = 7-70). For lymph node assessment, sensitivity of FDG-PET/CT is superior to CT with comparable specificity in 19 studies (n = 15-233). For detection of distant metastases, data from eight studies (n = 43-79) suggests that FDG-PET/CT is accurate, although comparative studies are lacking. Limited evidence (four studies, n = 19-50) suggests that FDG-PET/CT is not accurate for response evaluation of neoadjuvant chemotherapy. FDG-PET/CT incited change(s) in patient management in 18-68% of patients (five reports; n = 57-103). For detection of recurrence, seven studies (n = 29-287) indicated that FDG-PET/CT is accurate.

SUMMARY

Most studies evaluated FDG-PET/CT for lymph node assessment and reported higher sensitivity than CT, with comparable specificity. FDG-PET/CT showed incremental value to CECT for recurrence and often incited change(s) in patient management.

Performance of fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography imaging for lymph node staging in bladder and upper tract urothelial carcinoma: a systematic review

Objective: To evaluate the current literature on the accuracy of fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography (FDG PET-CT) for lymph node (LN) staging in urothelial carcinoma (UC), as robust evidence on the value of this technology in UC is still lacking.

Methods: The Medical Literature Analysis and Retrieval System Online (MEDLINE)/PubMed, Cochrane Library, and Scopus databases were searched for eligible studies. We included all original studies evaluating FDG PET-CT in bladder or upper tract UC. The search results were restricted to the English language, and included prospective and retrospective studies without time restriction. We included only studies reporting the sensitivity and specificity of FDG PET-CT in detecting UC LN metastases.

Results: We identified 23 articles meeting our inclusion criteria. In the preoperative setting, the sensitivity of FDG PET-CT for detecting LN metastases in patients with bladder cancer was widely variable ranging from 23% to 89%; the specificity ranged from 81% to 100%; and the overall accuracy ranged from 65% to 89%. During bladder cancer monitoring the sensitivity for detecting LN metastases ranged from 75% to 92% and the specificity ranged from 60% to 92%. The sensitivity for LN staging in upper tract UC ranged between 82% and 95%, with a specificity of 84–91%.

Conclusion: Despite the inconsistencies in sensitivity between the reports, FDG PET-CT seems to have a high specificity for LN staging in patients with UC. Future prospective, well-designed studies are necessary to evaluate the role of FDG PET-CT in UC management.

Abbreviations: FDG: fluoro-2-deoxy-D-glucose; LN: lymph node; PET: positron emission tomography; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-analyses; PSMA: prostate-specific membrane antigen; (N)(P)PV: (negative) (positive) predictive value; QUADAS-2: Quality Assessment of Diagnostic Accuracy Studies-2; SUV_max: maximum standard uptake value; (UT)UC: (upper urinary tract) urothelial carcinoma

How reliable are imaging techniques in aging males with bladder cancer?

INTRODUCTION

The aim of this study was to evaluate consistency between clinical lymph node positivity and pathological lymph node positivity in patients undergoing open radical cystectomy and pelvic lymph node dissection due to bladder cancer.

MATERIAL AND METHOD

A total of 135 patients who had open radical cystectomy, extended lymph node dissection, and clear preoperative contrast-enhanced abdominopelvic computed tomography (CT) or magnetic resonance imaging (MRI) images were included in the study. Positive clinical lymph nodes and positive pathological lymph nodeswere recorded. The largest positive clinical and pathological lymph nodeswere recorded. In terms of clinical lymph node involvement, compatibility between radiological findings and pathological results was evaluated.

RESULTS

In the CT group, the sensitivity was 25.81%, specificity was 95.45%, positive predictive value (PPV) was 66.67%, negative predictive value (NPV) was 78.50%, and accuracy was 77.31%. In the MRI group, the sensitivity was 50.00%, specificity was 100%, PPV was 100%, NPV was 76.92%, and accuracy was 81.25%. For consistency between pathological lymph nodes and clinical lymph nodes according to the imaging type, there was no statistically significant difference in the sensitivity, specificity, NPV, and accuracy rates between the imaging techniques (p > 0.05). However, the PPV was significantly higher in the MRI group than the CT group (100% vs.66.67%, respectively; p = 0.014).

CONCLUSION

Positive lymph nodes play a critical role in the prognosis of patients with bladder cancer and the sensitivity of contrast-enhanced abdominopelvic CT and MRI used routinely in clinical practice is low in lymph node detection. MRI seems more reliable than CT in lymph node detection.

The Role of 18F-FDG PET/CT in Guiding Precision Medicine for Invasive Bladder Carcinoma

Bladder cancer (BC) is the 10th most common cancer worldwide. Approximately one quarter of patients with BC have muscle-invasive disease (MIBC). Muscle-invasive disease carries a poor prognosis and choosing the optimal treatment option is critical to improve patients’ outcomes. Ongoing research supports the role of 2-deoxy-2-(18F)fluoro-D-glucose positron emission tomography (18F-FDG PET) in guiding patient-specific management decisions throughout the course of MIBC. As an imaging modality, 18F-FDG PET is acquired simultaneously with either computed tomography (CT) or MRI to offer a hybrid approach combining anatomical and metabolic information that complement each other. At initial staging, 18F-FDG PET/CT enhances the detection of extravesical disease, particularly in patients classified as oligometastatic by conventional imaging. 18F-FDG PET/CT has value in monitoring response to neoadjuvant and systemic chemotherapy, as well as in localizing relapse after treatment. In the new era of immunotherapy, 18F-FDG PET/CT may also be useful to monitor treatment efficacy as well as to detect immune-related adverse events. With the advent of artificial intelligence techniques such as radiomics and deep learning, these hybrid medical images can be mined for quantitative data, providing incremental value over current standard-of-care clinical and biological data. This approach has the potential to produce a major paradigm shift toward data-driven precision medicine with the ultimate goal of personalized medicine. In this review, we highlight current literature reporting the role of 18F-FDG PET in supporting personalized management decisions for patients with MIBC. Specific topics reviewed include the incremental value of 18F-FDG PET in prognostication, pre-operative planning, response assessment, prediction of recurrence, and diagnosing drug toxicity.

The Role of Imaging in Bladder Cancer Diagnosis and Staging

Bladder cancer (BC) is the most common cancer of the urinary tract in the United States. Imaging plays a significant role in the management of patients with BC, including the locoregional staging and evaluation for distant metastatic disease, which cannot be assessed at the time of cystoscopy and biopsy/resection. We aim to review the current role of cross-sectional and molecular imaging modalities for the staging and restaging of BC and the potential advantages and limitations of each imaging modality. CT is the most widely available and frequently utilized imaging modality for BC and demonstrates good performance for the detection of nodal and visceral metastatic disease. MRI offers potential value for the locoregional staging and evaluation of muscular invasion of BC, which is critically important for prognostication and treatment decision-making. FDG-PET/MRI is a novel hybrid imaging modality combining the advantages of both MRI and FDG-PET/CT in a single-setting comprehensive staging examination and may represent the future of BC imaging evaluation.

Preoperative chemotherapy in clinically node positive muscle invasive bladder cancer: Radiologic variables can predict response

PURPOSE

To evaluate pathologic downstaging after radical cystectomy and pelvic lymph node dissection for clinically lymph node positive urothelial bladder cancer and to determine optimal preoperative imaging variables in predicting pathologic nodal status.

METHODS

We identified all patients with clinically lymph node positive urothelial bladder cancer who underwent radical cystectomy and extended pelvic lymph node dissection with intent to cure at our institution. Patients were stratified based on pathologic node status to determine clinical associations and survival outcomes. Pre and post-chemotherapy CT scans were reviewed to characterize lymph node size and morphology. We also sought to determine associations between post-chemotherapy radiology variables and pathologic response.

RESULTS

We identified 130 patients with clinically node positive bladder cancer, out of which 76 (58.5%) received induction chemotherapy. Thirty three (43.4%) had pathologic T downstaging following chemotherapy, compared to 7 (12.9%) patients who had surgery alone (P< 0.0001). A complete nodal response (pN0) occurred in 31 (40.8%) patients post-chemotherapy, while 6 (11.1%) of those who received cystectomy alone ended up being pN0 (P< 0.0001). Median overall survival and recurrence-free survival were shorter in patients with pN+ versus pN0 disease (1.9 years vs. 12.8 years, P= 0.016 and 1.2 years vs. 4.3 years, P= 0.013, respectively). Review of 29 post chemotherapy CT scans showed that patients with pathologic nodal involvement had a greater median number of enlarged nodes (3.5 vs. 1, P= 0.038) and a greater median size of largest node (8.5 mm vs. 6.0 mm, P= 0.021) on imaging compared to those with complete pN0. Each 1 mm increase in size of the largest node on post-chemotherapy CT scan increased the chance of having pN+ disease by 1.57 (95% CI 1.02-2.44, P= 0.043). Using a median node size of 8 mm as a cut-off to predict pN+ disease provided a sensitivity and specificity of 72% and 80%, respectively (c-index = 0.761, P= 0.014). The positive predictive value for this cut-off was 87% (95% CI 58%-98%) and negative predictive value was 62% (32%-85%).

CONCLUSION

Patients with clinically node positive bladder cancer may have significant pN0 after induction chemotherapy. Our data suggest a post-chemotherapy CT scan with an 8 mm nodal size cut-off may be a better predictor of pathologic nodal status than more traditional measures.

Increasing use of positron emission tomography among medicare beneficiaries undergoing radical cystectomy

OBJECTIVE

To examine factors associated with PET scan use in the pre-operative evaluation of patients diagnosed with bladder cancer.

METHODS

Using SEER-Medicare data, we identified bladder cancer patients who underwent radical cystectomy from 2006 to 2011 (n = 4,138). The primary outcome was PET scan use within 6 months before surgery. To examine predictors of PET scan use, we fit a mixed logit model with health service area as a random effect to account for patients nested within health service areas. We also calculated the adjusted probability of use over time and examined variation among the highest volume surgeons.

RESULTS

Among the 4,138 patients, 406 (10%) received a pre-operative PET scan. The adjusted probability of a patient undergoing a PET scan increased from 0.04 in 2004 to 0.10 in 2011 (p < .001). Among the 78 highest volume surgeons, there was significant variation in PET scan use (p < .001). Patients with non-urothelial histology, measurement of alkaline phosphatase levels, and receipt of neoadjuvant chemotherapy were more likely to receive PET scan (all p < .05).

CONCLUSION

Use of PET prior to radical cystectomy doubled over a 5-year period, suggesting its increased use in patients with muscle-invasive bladder cancer, particularly those with high-risk disease. Whether its use is warranted and improves patient outcomes is not clear and requires further studies.

Preoperative imaging for locoregional staging of bladder cancer

Bladder cancer is the ninth most common cancer, expected to lead to an estimated 17,670 deaths in the United States in 2019. Clinical management and prognosis of bladder cancer mainly depend on the extent of locoregional disease, particularly whether bladder muscle is involved. Therefore, bladder cancer is often divided into superficial, non-muscle-invasive bladder cancer and muscle-invasive bladder cancer; the latter often prompts consideration for cystectomy. While precise staging prior to cystectomy is crucial, the optimal preoperative imaging modality used to stage the disease remains controversial. Transurethral resection of bladder tumor (TURBT) followed by computed tomography (CT) urography is the current recommended approach for staging bladder cancer but suffers from a high rate of understaging. We review the recent literature and compare different imaging modalities for assessing the presence of muscle invasion and lymph node involvement prior to cystectomy and highlight the advantages of each modality.

Integrated analysis of 18F-FDG PET/CT improves preoperative lymph node staging for patients with invasive bladder cancer

OBJECTIVES

Preoperative ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) is controversial to assess lymph node (LN) staging in patients with invasive bladder cancer. We proposed to use the maximum standardized uptake value (SUV_max) associated with axial-based LN size to improve the detection of regional LN metastasis.

METHODS

From May 2015 to May 2017, we prospectively included patients with urothelial bladder cancer who underwent radical cystectomy with extended pelvic LN dissection. All patients underwent preoperative ¹⁸F-FDG PET/CT staging before surgery. The gold standard comparator was the pathological examination of resected LNs. The data were reported on a regional per area- and patient-based model according to SUV_max values and axial-based LN size criteria.

RESULTS

In total, 1012 LNs were identified in 61 patients with clinically localized invasive bladder cancer who underwent radical cystectomy and extended pelvic LN dissection. Loco-regional involvement of 24 LN areas was confirmed in 17 patients. In per area analysis, diagnostic accuracy of PET/CT and CT alone were respectively 84% and 78% (p = 0.039). On patient-based analysis, combined PET/CT correctly classified pelvic LN status in 5/61 (+ 8%) additional patients using optimal thresholds compared to CT alone, with accuracies of 82% and 74%, respectively (p = 0.13).

CONCLUSION

Combining SUV_max and axial-based LN size criteria using ¹⁸F-FDG PET/CT improved the diagnostic accuracy for preoperative LN staging in patients with invasive bladder cancer, in per area analysis.

KEY POINTS

• Combining metabolical and morphological features using¹⁸F-FDG PET/CT improves the detection of malignant lymph node in patients with bladder cancer. • ¹⁸ F-FDG PET/CT may help for initial staging of patients with muscle invasive bladder cancer.

Evaluation of lymph node status in patients with urothelial carcinoma-still in search of the perfect imaging modality: a systematic review

While accurate lymph node status evaluation in urothelial carcinoma patients is essential for the correct disease staging and, hence, establishing the most beneficial treatment strategy, the diagnostic performance of routine imaging in regards to this issue is not satisfactory. For the purpose of this article, we systematically reviewed the contemporary literature on the sensitivity and specificity of particular imaging modalities which have been studied for detecting lymph node metastases in patients diagnosed with urothelial carcinoma. The evidence reviewed shows that computed tomography (CT), although recognized as the imaging modality of choice, is associated with marked limitations, resulting in its low sensitivity for lymph node involvement detection in urothelial carcinoma patients, with no study reporting a value higher than 46% using standard cut-off values. Markedly higher sensitivity rates may be achieved with magnetic resonance imaging (MRI), especially when using ultrasmall superparamagnetic iron oxide as the contrast agent, however, no uniform protocol has been systematically studied up to date. The vast majority of recent evidence concerns positron emission tomography (PET), which is being reported to improve the diagnostic performance of CT alone, as has been demonstrated in multiple articles, which investigated the accuracy of PET/CT at primary or post-treatment staging of urothelial carcinoma patients. However, there has been substantial heterogeneity in terms of methodology and results between those studies, making it premature to draw any definitive conclusions. The results of this review lead to a conclusion, that while CT, despite being not fully satisfactory, still remains the gold-standard method of imaging for staging purposes in urothelial carcinoma, other imaging modalities are under investigation, with promising results.

Low levels of PSMA expression limit the utility of 18F-DCFPyL PET/CT for imaging urothelial carcinoma

OBJECTIVE

To explore the clinical utility of PSMA-targeted 18F-DCFPyL PET/CT in patients with metastatic urothelial carcinoma.

METHODS

Three patients with metastatic urothelial carcinoma were imaged with 18F-DCFPyL PET/CT. All lesions with perceptible radiotracer uptake above background were considered positive. Maximum standardized uptake values were recorded for each detected lesion and findings on 18F-DCFPyL PET/CT were compared to those on conventional imaging studies. To further explore PSMA as a molecular target of urothelial carcinoma, RNA-sequencing data from The Cancer Genome Atlas were used to compare the relative expression of PSMA among cases of bladder cancer, prostate cancer, and clear cell renal cell carcinoma. Additionally, immunohistochemical staining for PSMA was performed on a biopsy specimen from one of the imaged patients.

RESULTS

18F-DCFPyL PET/CT allowed for the detection of sites of urothelial carcinoma, albeit with low levels of radiotracer uptake. Analysis of RNA-sequencing data revealed that bladder cancer had significantly lower levels of PSMA expression than both prostate cancer and clear cell renal cell carcinoma. Consistent with this observation, immunohistochemical staining of tissue from one of the imaged patients demonstrated a low level of neovascularization and nearly absent PSMA expression.

CONCLUSION

The relatively scant expression of PSMA by urothelial carcinoma likely limits the utility of PSMA-targeted PET imaging of this malignancy. Future research efforts should focus on the development of other molecularly targeted imaging agents for urothelial carcinoma.