Predictive impact of 2-18fluoro-2-deoxy-D-glucose positron emission tomography for residual postchemotherapy masses in patients with bulky seminoma

Optimal imaging techniques across the spectrum of testicular cancer

Over the years, several imaging techniques have been used in the diagnosis and management of testicular cancer. We compartmentalize disease stages into preorchiectomy, stage 1, initial stage 2 and 3 and postchemotherapy stage 2 and 3. We then elaborate on various imaging modalities that are relevant to each of these stages. We also describe evolving imaging tools that have shown promise. We attempt to provide a comprehensive review of these techniques over the spectrum of testicular cancer.

Role of 18F-Fluorodeoxyglucose Positron Emission Tomography in Children With Germ Cell Tumor After Chemotherapy

BACKGROUND/AIM

18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is a diagnostic tool widely used in adult oncology and some pediatric oncological settings. There are no established recommendations for the use of this imaging modality in pediatric malignant germ cell tumors (mGCT), however. Our aim is to evaluate the role of 18F-FDG PET/CT in the restaging of mGCT after chemotherapy in children and adolescents.

METHODS

We retrospectively reviewed patients with mGCT treated in Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP) centers who underwent 18F-FDG PET/CT between 2011 and 2021.

RESULTS

Seventeen patients (median age 13 y) were included in the study. In 14 patients, 18F-FDG PET/CT was performed at diagnosis; 12 showed pathologic uptake. The 2 18F-FDG PET/CT negative cases were histologically defined as yolk sac tumor (YST) and mixed (chorioncarcinoma, YST). Nine of the 12 patients who had pathologic 18F-FDG PET/CT at diagnosis repeated the examination after neoadjuvant chemotherapy, before, second look surgery. In 5 cases, no pathologic uptake was evident. Histology showed necrosis alone in 4 cases and necrosis and mature teratoma in 1. In 3 of the 6 cases with pathologic uptake (2 of 6 patients did not perform the examination at diagnosis), histology showed persistence of malignant component, whereas in the remaining 3 cases, necrosis and mature teratoma were present.

CONCLUSION

In our review of a series of children with mGCT, 18F-FDG PET/CT after neoadjuvant chemotherapy showed 1 of 5 false negatives and was unable to discriminate between residual malignant component and mature teratoma.

Treatment de-escalation for stage II seminoma

International Germ Cell Cancer Collaborative Group good-risk metastatic seminoma has cure rates of >95%. Within this risk group, patients with stage II disease exhibit the best oncological outcomes with the standard-of-care treatment strategies of radiotherapy or combination chemotherapy. However, these treatments can be associated with substantial early and late toxic effects. Therapy de-escalation aims to reduce treatment morbidity whilst preserving oncological outcomes. The evidence supporting such approaches is largely from non-randomized institutional data, and therefore this strategy is not recognized as standard of care. Current de-escalation approaches for stage II seminoma include single-agent chemotherapy, radiotherapy and surgery based on early data from clinical studies. Increased recognition of emerging data on treatment modification to reduce morbidity whilst maintaining cure rates and consideration of therapy de-escalation could improve patient survivorship outcomes.

Serum Levels of MicroRNA-371a-3p (M371) Can Predict Absence or Presence of Vital Disease in Residual Masses After Chemotherapy of Metastatic Seminoma

Background

Radiological evaluation of postchemotherapy residual masses of metastatic seminoma is characterized by poor diagnostic accuracy. Serum levels of microRNA-371a-3p (M371) involve high specificity and sensitivity for the primary diagnosis of seminoma. We evaluated if M371 levels can indicate the presence of vital disease in postchemotherapy residual masses in patients with metastatic seminoma.

Methods

Twenty-three seminoma patients (median age 52 years) with residual masses had posttreatment measurements of serum M371 levels (group A), fourteen of whom had measurements also beforehand. The posttreatment results were compared with the clinical outcome during follow-up. Eleven patients with complete remission after treatment of metastatic seminoma (group B) and 33 men with non-malignant testicular diseases (group C) served as controls. M371 serum levels were measured by quantitative real-time PCR using miR-30b-5p as endogenous control. An evaluation was performed with descriptive statistical methods.

Results

Twenty-two patients of Group A had uneventful follow-up so far, twenty-one of whom had M371 level <5, and one other had a mildly elevated level below relative quantity (RQ) = 10. One patient with a level of RQ = 26.2 rapidly progressed. The median posttreatment M371 level of the non-progressing patients of group A is not significantly different from the median level of the control group with complete remission (B). Before treatment, the median M371 levels in groups A and B were 507.6 and 143.9, respectively. In both groups, significant drops in M371 levels resulted from treatment.

Conclusion

Normal M371 serum levels at the time of completion of treatment of metastatic seminoma indicate the absence of vital seminoma in residual masses, while elevated levels >RQ = 10 predict the presence of disease. The optimal timing of M371 measurement after chemotherapy and the appropriate cutoff level still need to be determined. Based on the present results, measuring serum M371 levels involves the potential of a novel tool for assessing postchemotherapy residual masses of metastatic seminoma.

Vigilance is key: Metastatic teratoma in an enlarging retroperitoneal mass after treatment of advanced seminoma – a case report

We present the case of a patient with pure seminoma in the orchiectomy specimen with retroperitoneal mass and a minimally elevated alpha fetoprotein (AFP). The patient received chemotherapy with positron emission tomography (PET) imaging demonstrating minimal fluorodeoxyglucose (FDG) uptake consistent with no viable tumour. Subsequent imaging revealed slow growth in the residual mass with a mildly elevated fluctuating AFP. A robotic-assisted laparoscopic retroperitoneal lymph node dissection was performed revealing metastatic teratoma. This case illustrates the potential for a missed or ‘burned out’ occult NSGCT in a patient with pure seminoma and the importance of post-treatment surveillance. In advanced seminoma, PET may be used to distinguish viable tumour from necrosis in post-chemotherapy residual masses. However, it is unable to distinguish between teratoma and necrosis in non-seminomatous germ cell tumours (NSGCT). Minimally elevated AFP could be a normal variant or signify a component of NSGCT in such cases.

Level of evidence: 4

Prognostic Role of Early Interim Fluorodeoxyglucose Positron Emission Tomography in Patients With Advanced Seminoma Undergoing Standard Treatment

BACKGROUND

Patients with advanced seminoma have an exceedingly favorable prognosis. Studies aiming to reduce the total treatment burden and side effects in patients with well-defined disease and very good prognosis are warranted.

PATIENTS AND METHODS

In a prospective observational study, patients with advanced stage seminoma were treated with bleomycin, etoposide, and cisplatin (BEP) or EP according to guidelines. Fluorodeoxyglucose with positron emission tomography and computed tomography (FDG-PET/CT) examinations were performed at baseline, after 2 cycles (PET/CT2) in all patients, and after chemotherapy at the physician's discretion. Disease response to treatment assessed by PET/CT was qualitatively evaluated by 2 independent nuclear medicine physicians. Contrast-enhanced CT scans were also performed according to guidelines (at baseline, after treatment, during follow-up). The study's primary endpoint was to evaluate the association between PET/CT2 findings and relapse-free survival.

RESULTS

From January 2009 to January 2017, a total of 75 consecutive patients were enrolled, of whom 70 were included for analysis. The clinical disease stage was IIA-B and IIC-III in 40% and 60%, respectively. By local assessment, 46 PET/CT2 scans (65.7%) were reported as negative, and 46% of these patients had stage IIC-III disease. Five-year relapse-free survival of PET/CT2-positive patients was 75% (95% confidence interval, 60-95) compared to 97.8% (95% confidence interval, 93.7-100) of PET/CT2-negative patients (P = .002). In univariate analyses, PET/CT2 was significantly associated with relapse-free survival (P = .02).

CONCLUSIONS

No residual FDG uptake after 2 cycles of conventional chemotherapy is prognostic in advanced seminoma, but it may be useful to optimize the standard prognostic risk groups and may be tested within larger prospective clinical trials of chemotherapy deescalation.

[Positron emission tomography in germ cell tumors in men : Possibilities and limitations]

BACKGROUND

Conventional radiographic imaging may fail to safely distinguish clinical stage I from stage IIA germ cell cancer, to localize isolated tumor marker relapses, and to equivocally identify the viability of postchemotherapy residual masses.

OBJECTIVES

To provide an overview of the diagnostic value and limitations of functional imaging by positron emission tomography with 2‑deoxy-2-[fluorine-18]fluoro-D-glucose with computed tomography (¹⁸F-FDG-PET-CT) in male germ cell cancer.

MATERIALS AND METHODS

A narrative review based on a literature search of PubMed/MEDLINE for original articles published from 1990-2018 and conference proceedings of ASCO (American Society of Clinical Oncology) and EAU (European Association of Urology) annual meetings 2014-2017 is presented.

RESULTS

¹⁸F-FDG-PET-CT does not improve diagnostic accuracy compared to conventional CT imaging clinical stage (CS) I disease. Particularly PET-negativity of postchemotherapy residual masses of seminomas >3 cm in size guide decision-making against further additional treatment. Even PET-positive residues must not result in relapse. For nonseminoma, the value of PET imaging is reduced by potential mature teratoma components, which are commonly PET negative.

CONCLUSIONS

Current guidelines recommend ¹⁸F-FDG-PET-CT 6-8 weeks postchemotherapy for viability assessment of seminoma residues >3 cm in size. Exceptional circumstances, in which ¹⁸F-FDG-PET-CT may be helpful, include: (1) detection of active disease in CS IS, (2) viability assessment of residual masses >1 cm where complete secondary resection is impossible, (3) staging at marker relapse with unconspicuous conventional CT scan, (4) early response assessment during chemotherapy.

Saudi Oncology Society and Saudi Urology Association combined clinical management guidelines for testicular germ cell tumors

This is an update to the previously published Saudi guidelines for the evaluation, medical, and surgical management of patients diagnosed with testicular germ cell tumors. It is categorized according to the stage of the disease using the tumor-node-metastasis staging system 7(th) edition. The guidelines are presented with supporting evidence level, they are based on comprehensive literature review, several internationally recognized guidelines, and the collective expertise of the guidelines committee members (authors) who were selected by the Saudi Oncology Society and Saudi Urological Association. Considerations to the local availability of drugs, technology and expertise have been regarded. These guidelines should serve as a roadmap for the urologists, oncologists, general physicians, support groups, and health care policy makers in the management of patients diagnosed with testicular germ cell tumors.

The role of 18F-FDG PET/CT in the management of testicular cancers

OBJECTIVES

The aim of this study was to determine the utility of fluorine-18 fluorodeoxyglucose PET/computed tomography ((18)F-FDG PET/CT) in managing testicular cancer.

PATIENTS AND METHODS

Sixty-two patients (29 seminoma, 28 nonseminoma and five mixed) underwent 75 (18)F-FDG PET/CT scans (16 scans for primary staging, 44 for residual masses and 15 for rising tumour markers). Follow-up histology, clinical scans and tumour marker results were included for retrospective analysis.

RESULTS

(i) Primary staging: eight of 11 patients with equivocal CT scans had true-negative (18)F-FDG PET/CT scans. Five high-risk patients with normal stage 1 CT scans had negative (18)F-FDG PET/CT scans, but two subsequently relapsed. (ii) Residual masses: of the 20 scans interpreted as showing viable disease, five were false positive. Nineteen scans were negative (18 true negative and one false negative). (iii) Rising tumour markers: of the 15 scans, two were false negative and 13 were true positive.

CONCLUSION

(18)F-FDG PET/CT is helpful when primary staging CT scans are equivocal but insufficiently sensitive to predict relapse in high-risk patients with normal CT scans. With residual masses, a negative scan is rarely associated with relapse. (18)F-FDG PET/CT is helpful in defining recurrent disease in the majority of patients with rising tumour markers and negative CT scans.

Evolving role of positron emission tomography (PET) in urological malignancy

We present a review on the increasing indications for the use of positron emission tomography (PET) in uro-oncology. In this review we describe the details of the different types of PET scans, indications for requesting PET scans in specific urological malignancy and the interpretation of the results.

PET/Computed Tomography in Renal, Bladder, and Testicular Cancer

Imaging plays an important role in the clinical management of cancer patients. Hybrid imaging with PET/computed tomography (CT) is having a broad impact in oncology, and in recent years PET/CT is beginning to have an impact in urooncology. In both bladder and renal cancers, there is a need to study the efficacy of other tracers than F-18 fluorodeoxyglucose (FDG), particularly tracers with limited renal excretion. Thus, new tracers are being introduced. This review focuses on the clinical role of FDG and other PET agents in renal, bladder, and testicular cancers.

Saudi oncology society and Saudi urology association combined clinical management guidelines for testicular germ cell tumors

In this report, updated guidelines for the evaluation, medical, and surgical management of germ cell tumor of testes are resented. They are categorized according the stage of the disease using the tumor-node-metastasis staging system 7(th) edition. The recommendations are presented with supporting level of evidence.

Diagnostic performance of fluorine-18-fluorodeoxyglucose positron emission tomography in the postchemotherapy management of patients with seminoma: systematic review and meta-analysis

Objective. To meta-analyze published data about the diagnostic performance of fluorine-18-Fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and PET/computed tomography (PET/CT) in the postchemotherapy management of patients with seminoma. Methods. A comprehensive literature search of studies published through January 2014 on this topic was performed. All retrieved studies were reviewed and qualitatively analyzed. Pooled sensitivity and specificity, positive and negative predictive values (PPV and NPV), accuracy, and area under the summary ROC curve (AUC) of ¹⁸F-FDG-PET or PET/CT on a per examination-based analysis were calculated. Subgroup analyses considering the size of residual/recurrent lesions were carried out. Results. Nine studies including 375 scans were selected. The pooled analysis provided the following results: sensitivity 78% (95% confidence interval (95% CI): 67–87%), specificity 86% (95% CI: 81–89%), PPV 58% (95% CI: 48–68%), NPV 94% (95% CI: 90–96%), and accuracy 84% (95% CI: 80–88%). The AUC was 0.90. A better diagnostic accuracy of ¹⁸F-FDG-PET or PET/CT in evaluating residual/recurrent lesions >3 cm compared to those <3 cm was found. Conclusions. ¹⁸F-FDG-PET and PET/CT were demonstrated to be accurate imaging methods in the postchemotherapy management of patients with seminoma; nevertheless possible sources of false-negative and false-positive results should be considered. The literature focusing on this setting still remains limited and cost-effectiveness analyses are warranted.

Platinum-based Chemotherapy in Primary Advanced Seminoma-a Retrospective Analysis: Treatment Results at the Northern Israel Oncology Center (1989-2010)

OBJECTIVE

Over the past 30 years, great strides have been made in the treatment of disseminated testicular tumors. Despite the low number of patients and the rarity of studies concerning primary advanced seminoma, the efficacy of chemotherapy is clear, mainly 3-4-cisplatin-based chemotherapy. Aiming to contribute to the understanding and implementation of proper chemotherapeutic management in advanced seminoma patients, we retrospectively summarized our experience with 26 patients who were referred for platinum-based chemotherapy, post-orchiectomy to the Northern Israel Oncology Center between 1989 and 2010. Response rate, side effects, and long-term outcome were investigated.

METHODS

Before chemotherapy, meticulous staging was done, including tumor markers (B-human chorionic gonadotropin (B-HCG), alpha-fetoprotein (AFP), and lactic dehydrogenase (LDH)), and abdominal and pelvic computerized tomography (CT) scans were carried out.

RESULTS

All 26 treated patients achieved complete remission, clinically and symptomatically, with normalization of their CT scans. At a median follow-up of 120 months (range, 24-268 months) all patients are alive, without evidence of recurrent disease. One patient whose disease recurred twice achieved a third complete remission following salvage treatment with high-dose chemotherapy and autologous peripheral stem cell transplantation. Another patient, who preferred surveillance, relapsed abdominally after 9 months but achieved long-standing complete remission with cisplatin-based chemotherapy. Both these patients are alive with no evidence of disease. Three patients recovered uneventfully from bleomycin-induced pneumonitis.

CONCLUSIONS

Advanced seminoma is a highly curable disease using platinum-based chemotherapy. Our study confirms the efficacy and safety of cisplatin-based chemotherapy in the treatment of advanced seminoma.

Isolated femoral muscle and bone metastases rarely encountered in testicular seminoma

Isolated muscle and bone metastases are rarely encountered in patients with testicular seminomas. In the present study, a patient who was admitted with pain, loss of motion, and swelling in the right leg 20 months following surgery for stage I seminoma was presented. Hypermetabolic lesion was detected in the right femoral muscle and bone via positron emission tomography. After the presence of metastasis from seminoma was confirmed by biopsy, bleomycin, cisplatin, and etoposide, combination chemotherapy was administered to the patient.

2-¹⁸fluoro-deoxy-D-glucose positron emission tomography (FDG-PET) for postchemotherapy seminoma residual lesions: a retrospective validation of the SEMPET trial

BACKGROUND

2-¹⁸fluoro-deoxy-D-glucose positron emission tomography (FDG-PET) has been recommended in international guidelines in the evaluation of postchemotherapy seminoma residuals. Our trial was designed to validate these recommendations in a larger group of patients.

PATIENTS AND METHODS

FDG-PET studies in patients with metastatic seminoma and residual masses after platinum-containing chemotherapy were correlated with either the histology of the resected lesion(s) or the clinical outcome.

RESULTS

One hundred and seventy seven FDG-PET results were contributed. Of 127 eligible PET studies, 69% were true negative, 11% true positive, 6% false negative, and 15% false positive. We compared PET scans carried out before and after a cut-off level of 6 weeks after the end of the last chemotherapy cycle. PET sensitivity, specificity, negative predictive value (NPV), and positive predictive value were 50%, 77%, 91%, and 25%, respectively, before the cut-off and 82%, 90%, 95%, and 69% after the cut-off. PET accuracy significantly improved from 73% before to 88% after the cut-off (P=0.032).

CONCLUSION

Our study confirms the high specificity, sensitivity, and NPV of FDG-PET for evaluating postchemotherapy seminoma residuals. When carried out at an adequate time point, FDG-PET remains a valuable tool for clinical decision-making in this clinical setting and spares patients unnecessary therapy.

[Assessment of residual tumours after systemic treatment of metastatic seminoma: ¹⁸F-2-fluoro-2-deoxy-D-glucose positron emission tomography - meta-analysis of diagnostic value]

BACKGROUND

Meta-analysis evaluating the accuracy and sensitivity of FDG (2-[(18)F]-fluoro-2-deoxy-D-glucose) positron emission tomography (PET) to predict viable residual tumours in patients with metastatic seminoma.

MATERIAL AND METHODS

Altogether 5 studies with 130 patients were identified. Both FDG PET and the size of the residual lesions on conventional computed tomography (CT; lesions either ≤ or > 3 cm) were correlated with the presence or absence of viable residual tumour.

RESULTS

The specificity (92 vs 59%), sensitivity (72 vs 63%), positive (70 vs 28%) and negative (93 vs 86%) predictive value of FDG PET were superior to data obtained by assessing residual tumour size (either ≤ or > 3 cm) applying CT scans alone.

CONCLUSION

In view of the data currently available, FDG PET seems to be a clinically useful predictor of viable tumour in post-chemotherapy residuals of pure seminoma.

Saudi Oncology Society clinical management guidelines for testicular germ cell tumors

In this report, guidelines for the evaluation, medical and surgical management of testicular germ cell tumors is presented. It is categorized according to the stage of the disease using the tumor node metastasis staging system, 7th edition. The recommendations are presented with supporting level of evidence.

PET in testicular cancer

Testicular cancer is a rare tumor, subdivided into seminomatous and nonseminomatous tumors. Whereas there are no serum tumor markers in the first group, they are present in nonseminomatous tumors, and are also important prognostic factors. Overall, the prognosis for testicular cancers is good, which makes the choice of accurate treatment intensity between under- and overtreatment often difficult. Residual masses in advanced clinical stages occur frequently but are nonvital tissue. PET with F-18 FDG has no defined role in imaging of primary tumors where CT is the first-choice imaging modality. For assessing the success of chemotherapy in the presence of residual masses, especially in pure seminoma, F-18 FDG PET is an important tool. In nonseminomatous tumors, it is hampered by the false-negative results in mature teratoma, for which reason false-negative results are a common problem. F-18 FDG PET performs best in predicting relapse in seminoma residuals larger than 3 cm. So far, no alternative to F-18 FDG for PET imaging of testicular cancer has been found. PET-CT has not yet been proven to be superior to PET alone in testicular cancer.

Fusion imaging: a novel staging modality in testis cancer

Objective: Computed tomography and chest radiographs provide the standard imaging for staging, treatment, and surveillance of testicular germ cell neoplasms. Positron emission tomography has recently been utilized for staging, but is somewhat limited in its ability to provide anatomic localization. Fusion imaging combines the metabolic information provided by positron emission tomography with the anatomic precision of computed tomography. To the best of our knowledge, this represents the first study of the effectiveness using fusion imaging in evaluation of patients with testis cancer.

Methods: A prospective study of 49 patients presenting to Walter Reed Army Medical Center with testicular cancer from 2003 to 2009 was performed. Fusion imaging was compared with conventional imaging, tumor markers, pathologic results, and clinical follow-up.

Results: There were 14 true positives, 33 true negatives, 1 false positive, and 1 false negative. Sensitivity, specificity, positive predictive value, and negative predictive value were 93.3, 97.0, 93.3, and 97.0% respectively. In 11 patient scenarios, fusion imaging differed from conventional imaging. Utility was found in superior lesion detection compared to helical computed tomography due to anatomical/functional image co-registration, detection of micrometastasis in lymph nodes (pathologic nodes < 1cm), surveillance for recurrence post-chemotherapy, differentiating fibrosis from active disease in nodes < 2.5cm, and acting as a quality assurance measure to computed tomography alone.

Conclusions: In addition to demonstrating a sensitivity and specificity comparable or superior to conventional imaging, fusion imaging shows promise in providing additive data that may assist in clinical decision-making.

[18F]Fluorodeoxyglucose Positron Emission Tomography in Nonseminomatous Germ Cell Tumors After Chemotherapy: The German Multicenter Positron Emission Tomography Study Group

Purpose

In patients with metastatic nonseminomatous germ cell cancer (NSGCT), residual masses after chemotherapy (CTX) can consist of vital carcinoma, mature teratoma, or necrosis. This prospective trial has evaluated the accuracy of [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) for the prediction of histology compared with computed tomography (CT) and serum tumor markers (STM).

Patients and Methods

A total of 121 patients with stage IIC or III NSGCT scheduled for secondary resection after cisplatin-based CTX were included. FDG-PET was performed after completion of CTX. All results were confirmed by histopathology and correlated to STM and CT.

Results

Prediction of tumor viability with FDG-PET was correct in 56%, which did not reach the expected clinically relevant level of 70%, and was not better than the accuracy of CT (55%) or STM (56%). Sensitivity and specificity of FDG-PET were 70% and 48%. The positive predictive values were not significantly different (55%, 61%, and 59% for CT, STM, and PET, respectively). Judging only vital carcinoma as a true malignant finding, the negative predictive value increased to 83% for FDG-PET.

Conclusion

The presence of vital carcinoma and mature teratoma is common (55%) in residual masses in patients with NSGCT, and CT and STM cannot reliably predict absence of disease. In contrast to prior studies, this prospective trial, which is the only with histologic confirmation in all patients, demonstrated that FDG-PET is unable to give a clear additional clinical benefit to the standard diagnostic procedures, CT and STM, in the prediction of tumor viability in residual masses.

Positron emission tomography (PET) in the urooncological evaluation of the small pelvis

Positron emission tomography (PET) with the use of ((18)F)2-fluoro-D: -2-desoxyglucose (FDG) has been investigated to be a highly sensitive and specific imaging modality in the diagnostic of primary and recurrent tumors and in the control of therapies in numerous non-urologic cancers. The aim of this review is to validate the significance of PET as a diagnostic tool in malignant urological tumors of the small pelvis. A systematic review of the current literature concerning the role of PET for malignant prostate, testicular and bladder tumors was carried out. The data indicate no additional role for PET in comparison with conventional imaging in tumor detection and local staging for prostate, bladder or testicular cancer. Tumor recurrence in prostate cancer seems to be more effectively identified with acetate and choline than with FDG, but this effect is more pronounced with higher PSA values. The value of PET in the identification of metastatic disease in either tumor entity can not be finally outlined as the clinical data are partly missing, controversial or in the process of evaluation. FDG-PET can be regarded as accepted imaging modality in the restaging of seminomatous germ cell tumors after chemotherapy.

Molecular Positron Emission Tomography and PET/CT Imaging in Urological Malignancies

OBJECTIVES

Positron emission tomography (PET) provides unique insights into molecular pathways of diseases. PET using [F-18]-fluorodeoxyglucose (FDG) has gained increasing acceptance for the diagnosis, staging, and treatment monitoring of various tumour types. The aim of this review is to provide an update on the current status of molecular PET and PET/CT imaging in urological malignancies.

METHODS

The current literature on PET and PET/CT imaging was reviewed and summarized for prostate cancer, bladder cancer, renal cell carcinoma, and germ cell tumours.

RESULTS

Depending on the radiotracer used, PET offers diagnostic information based on glucose, choline or amino acid metabolism and has also been applied to imaging tumour cell proliferation and tissue hypoxia in urological malignancies. The diagnostic performance of FDG-PET is hampered by the renal excretion of FDG and by the low metabolic activity often seen in tumours such as prostate cancer. However, new PET tracers including radiolabelled choline and acetate may offer an alternative approach. There is consistent evidence that FDG-PET provides important diagnostic information in detecting metastatic and recurrent germ cell tumours and it might offer additional information in the staging and restaging of bladder and renal cancer.

CONCLUSIONS

Although PET imaging has been shown to be a clinically useful tool, its application in urological malignancies still needs to be fully determined by larger prospective trials. The introduction of novel PET radiopharmaceuticals along with the new technology of PET/CT will likely change the future role of molecular imaging in urological malignancies.

The Role of Imaging in the Surveillance of Urologic Malignancies

Urologic malignancies are common, accounting for approximately 25% of all new cancer cases in the United States. Patients with urologic malignancies require long-term surveillance to detect progression or recurrence as early as possible. The urologist is faced with the task of balancing patient safety and cost-effectiveness, while finding the most practical follow-up regimen. For each urologic malignancy, this article reviews the commonly used radiologic techniques for surveillance and offers recommended follow-up schedules.

Positron emission tomography: clinical applications in oncology. Part 2

This review continues from a previous review on this topic, which was published in the December issue. In that review, the role of positron emission tomography in lung cancer, lymphoma, breast cancer, head and neck cancer, gastroesophageal cancer, colorectal cancer, malignant melanoma, bone tumors and ovarian cancer was discussed. In this review, the role of positron emission tomography in other malignancies, such as gynecological malignancies other than ovary, pancreatic cancer, hepatocellular cancer, gastrointestinal tumors, urological malignancies, neuroendocrine tumors, adrenocortical tumors, soft-tissue sarcomas, pituitary and brain tumors, is discussed.

Republication of SEMPET trial data?

Becherer and colleagues' report in the European Journal of Radiology of their interesting data on the use of FDG PET in the evaluation of residual masses in seminoma patients is extremely similar to the data that the same authors published in 2004 in the Journal of Clinical Oncology. It would be very helpful to know whether these are the same patients being presented again or a new multicenter study of the same size asking the same question. Oddly, the authors do not acknowledge their prior report even though it was published the same month that the report to the European Journal of Radiology was submitted for review. It would be helpful if the authors explained what the 2005 report adds to the 2004 report for those of us trying to assess the role of FDG PET in this patient population. At this point in time, it appears that there are two studies that have been completed, including a negative trial from the United States and a positive trial (now published three times) from Europe.

Postchemotherapy residual masses in advanced seminoma: current management and outcomes

Although pure testicular seminoma is most often confined to the testis, it can present with advanced-stage bulky retroperitoneal metastases in nearly a quarter of cases. While highly treatable with cisplatin-based chemotherapy, up to 80% of patients with advanced disease are found to have a radiographically detectable residual mass after chemotherapy. The management of these postchemotherapy residual masses remains controversial. Surgical resection is technically challenging due to a desmoplastic reaction resulting from seminoma treatment and regression. In addition, these residual masses often demonstrate a protracted period of regression that can span several months to years. Surveillance protocols, therefore, may be appropriate for most patients. Several retrospective studies have supported surgical resection only for discrete, well-delineated masses over 3 cm in size. Despite the highly radiosensitive nature of seminoma, radiation therapy in this setting has not been shown to provide significant benefit, and may limit the tolerability of subsequent salvage chemotherapy. The incorporation of noninvasive imaging modalities, such as positron emission tomography, into the management algorithm may better delineate the presence of viable residual tumor and thus allow better risk stratification.

Nuclear Medicine Studies of the Prostate, Testes, and Bladder

During the last decade, there has been a significant advancement in imaging of urologic diseases. Transrectal ultrasound (TRUS), computerized tomography (CT), magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and positron emission tomography (PET) are still experiencing new developments in urology. Despite these many technological advances, the initial diagnostic procedure for a patient with suspected prostate cancer (PC) is multiple site blind prostate biopsies. There is a need for a noninvasive metabolic imaging modality to direct the site of biopsy to decrease the sampling error. MRS seems promising but as it is a costly and more time-consuming test, further studies are needed to evaluate its clinical utility. Currently, PET does not play any role to direct biopsy. Acetate and choline appear to be better tracers than FDG for the detection of a prostate lesion, however, further well-organized studies are needed before any of these agents can be used clinically. Incidental detection of intense focal uptake in the prostate during whole body PET scanning should be evaluated with prostate-specific antigen (PSA) and TRUS-guided biopsy. Although FDG is inferior to other tracers for primary staging, it may be useful in selected patients with suspected high-grade cancer. The role of ProstaScint scan is still controversial for detection of recurrent PC. This study may be helpful for evaluating nodal metastases when PSA is elevated and bone scan is negative. Bone scan remains the study of choice when bone metastases are suspected (PSA>15-20 ng/mL+/-bone pain). Acetate and choline provide better accuracy than FDG in the detection of local soft tissue disease, nodal involvement, and distant metastases. High FDG uptake may be indicative of more aggressive and possibly androgen-independent disease. PET/CT with any of the above PET tracers will most likely be preferred to the PET scan alone due to better localization of a hot lesion in PET/CT. Nuclear medicine studies also have been used to evaluate acute scrotum and testicular neoplasms. Scrotal scintigraphy has lost its popularity to Doppler ultrasound in the evaluation of the acute scrotum. In testicular tumors, FDG-PET appears to be superior to conventional imaging modalities in initial staging, detection of residual/recurrence, and monitoring treatment response. Tumor markers after treatment occasionally are elevated and cannot locate the site of recurrence, FDG-PET can play a very important role in this regard. Nuclear medicine studies also have been used to evaluate diseases of the urinary bladder. Radionuclide cystography is more sensitive and has less than 1/20 the radiation exposure of the conventional contrast enhanced micturating cystourethrogram (MCU). However, the utility of FDG-PET in the evaluation of bladder cancer seems to be limited to the evaluation of distant metastases. 11C-Methionine and choline may be a better option for local and nodal disease due to their negligible excretion in the urine.

[Lymphadenectomy for testicular cancer. Diagnostic and prognostic significance as well as therapeutic benefit]

The rationale to perform retroperitoneal lymph node dissection (RPLND) in testicular cancer depends on the clinical stage and previous therapy. Thus, it can be performed either with diagnostic, prognostic, or therapeutic intention. In verified clinical stage I nonseminoma, RPLND provides one of three adjuvant options. To verify the clinical stage pathologically, surgery is done for diagnostic reasons, since CT scanning provides a false-negative staging in up to 30%. In higher stage lesions RPLND is a therapeutic procedure. The importance, however, of RPLND in clinical stage I nonseminoma is decreasing, since prognostic factors are available to stratify patients with either low or high risk for recurrence. Thus, these patients are selected for surveillance (low risk) or adjuvant chemotherapy (high risk). RPLND after chemotherapy is done for resection of residual tumor with a therapeutic intention. The histology of the residual mass is of prognostic importance and may help define further therapy. Resection of retroperitoneal metastases in patients with chemorefractory tumors is curative in about 25%.

FDG-PET in the management of germ cell tumor

Germ cell tumor is the most common malignancy in young men. The cure rate of these patients has tremendously increased in the cisplatin era, and recent results have indicated that the management of patients with GCT is still improving. The use of FDG-PET in the management of patients with GCT has been recently investigated. This report attempts to comprehensively review new advances and delineate the potential applications of FDG-PET in GCT.

FDG PET is superior to CT in the prediction of viable tumour in post-chemotherapy seminoma residuals

AIM

In advanced seminoma the management of residuals after completion of chemotherapy is controversial. Some centres routinely perform surgery for lesions > or =3 cm diameter, others recommend surgery solely if the residual fail to shrink or show even growth. This study prospectively investigates whether FDG PET can improve the prediction of viable tumour in post-chemotherapy seminoma residuals.

MATERIALS AND METHODS

After an expansion of a previous study population, 54 patients from eight centres with metastatic seminoma and a CT-documented mass after chemotherapy were included in the study. Six patients were excluded from evaluation because of protocol violations. After PET, the patients underwent either surgery or were followed clinically. On follow-up the lesions were considered to be non-viable when there was unequivocal shrinking, or when the lesion remained morphologically stable for at least 24 months. Any lesion growth was assumed to be malignant. PET results were compared to CT discrimination (< or > or =3 cm) of the residual masses.

RESULTS

Fifty-two PET scans were evaluable. After adequate chemotherapy, there were 74 CT-documented residual masses ranging in size from 1 to 11 cm (median, 2.2 cm). Their dignities were confirmed histologically in 13 lesions, or by follow-up CT in 61 lesions. Four of forty-seven lesions <3 cm and 11/27 lesions > or =3 cm were viable. PET was true positive in one lesion <3 cm and in 11 lesions > or =3 cm, false negative in three lesions <3 cm, and true negative in 59 lesions (43 lesions <3 cm). No PET scan was false positive. In detecting viability the sensitivity and specificity was 73% (95% CI, 44-88), and 73% (59-83), respectively, for CT (< or > or =3 cm); and 80% (51-95), and 100% (93-100), respectively, for PET (specificity, P < 0.001).

CONCLUSION

In post-chemotherapy seminoma residuals, a positive PET is highly predictive for the presence of viable tumour. The specificity of PET is significantly higher than that of CT when using a > or =3 cm cut-off. A negative PET scan is excellent for the exclusion of disease in lesions > or =3 cm, with a somewhat higher sensitivity than CT (n.s.). PET can contribute to the management of residual seminoma lesions, especially in terms of avoiding unnecessary additional treatment for patients with lesions > or =3 cm.

[The value of 18F-fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG PET) in diagnosis of neoplastic diseases]

Positron emission tomography (PET) has the ability to detect cancer based on molecular and biochemical processes within the tumor tissues. The most widely used radiotracer in oncology at this time is the glucose analogue 18F-fluoro-2-deoxy-D-glucose (18F-FDG). Like glucose, 18F-FDG is transported into cells by a glucose transporter protein and rapidly converted into 18F-FDG-6-phosphate. PET imaging with 18F-FDG is able to diagnose, stage, and restage many cancers with accuracies ranging from 80% to 90%. Responses to therapy can be identified earlier and with greater accuracy than is possible with anatomic imaging modalities. The prognostic information available through 18F-FDG PET is superior to that of conventional imaging for many cancers. The aim of this review article is to show the most promising clinical indications for the use of PET in oncology.

Positron emission tomography in uro-oncology

Positron emission tomography (PET) in uro-oncology has been one of the slowest areas to develop. There are problems because of the excretion of tracer through the renal tract. Its use in prostate cancer has generally being disappointing, with PET being unable to differentiate malignancy from benign prostatic hypertrophy. In more advanced disease and in the search for the site of recurrence, PET can be of more use. Also, new tracers may prove to be more effective. PET has been shown to be of value in testicular cancer, particularly in defining recurrent disease in residual masses and in patients with raised markers. There is a clear place for PET in some of these cases. Early studies at staging are promising but more work is required to define its exact place. In renal and bladder cancer, PET may be a useful adjunct to conventional imaging in difficult cases and may assist in local staging. In all tumours it is valuable to differentiate fibrosis from recurrent disease in the treatment bed, an area of difficulty for CT/MR.

18F-fluorodeoxyglucose positron emission tomography in evaluation of germ cell tumor after chemotherapy

OBJECTIVES

To evaluate the role of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) in the assessment of germ cell tumors after chemotherapy.

METHODS

We reviewed patients' records for the histologic findings and clinical outcome. 18F-FDG PET results were correlated with tissue histologic features where available; and if not available, the correlation was with the clinical outcome.

RESULTS

A total of 45 PET studies were performed on 38 patients (age range 19 to 64 years, median 31). All patients had received chemotherapy. In the nonseminomatous germ cell tumor (NSGCT) group, of the 31 patients with one scan, 18 PET scans were reported as positive, with only 2 not having active disease. Of the 12 negative scans, 6 showed teratoma, 1 tumor, and 5 did not show active disease. The equivocal scan revealed thyroid adenoma. In the seminoma group, the PET scans correlated well with the clinical and histologic outcomes. Four patients underwent salvage chemotherapy, and in this subgroup, the PET findings also correlated with the outcome.

CONCLUSIONS

(18)F-FDG PET is a promising tool as an adjunct to current imaging techniques in detecting residual viable germ cell tumor after chemotherapy. In NSGCT, a positive PET scan was accurate in 16 of 18 patients, although negative PET studies did not exclude the presence of disease, mainly because of the presence of teratoma. In seminoma, a negative 18F-FDG PET study correlated with a favorable clinical outcome. PET was also predictive of the response to salvage chemotherapy and was highly specific for active tumor in both NSGCT and seminoma.