Does positron emission tomography using 18-fluoro-2-deoxyglucose improve clinical staging of testicular cancer?--Results of a study in 50 patients

Clinical applications of PET in oncology

Positron emission tomography (PET) provides metabolic information that has been documented to be useful in patient care. The properties of positron decay permit accurate imaging of the distribution of positron-emitting radiopharmaceuticals. The wide array of positron-emitting radiopharmaceuticals has been used to characterize multiple physiologic and pathologic states. PET is used for characterizing brain disorders such as Alzheimer disease and epilepsy and cardiac disorders such as coronary artery disease and myocardial viability. The neurologic and cardiac applications of PET are not covered in this review. The major utilization of PET clinically is in oncology and consists of imaging the distribution of fluorine 18 fluorodeoxyglucose (FDG). FDG, an analogue of glucose, accumulates in most tumors in a greater amount than it does in normal tissue. FDG PET is being used in diagnosis and follow-up of several malignancies, and the list of articles supporting its use continues to grow. In this review, the physics and instrumentation aspects of PET are described. Many of the clinical applications in oncology are mature and readily covered by third-party payers. Other applications are being used clinically but have not been as carefully evaluated in the literature, and these applications may not be covered by third-party payers. The developing applications of PET are included in this review.

The role of positron emission tomography in germ cell cancer

Positron emission tomography (PET) is a non-invasive tool for imaging regional metabolic processes, which adds another dimension to current anatomy-derived imaging techniques, i.e. metabolic imaging. To date, 2-(18)fluoro-2-deoxy-D-glucose (FDG) has been the only tracer used for imaging germ cell tumors (GCT), which can be distinguished from normal tissue by their different glucose utilization. However, FDG PET has several limitations: (1) inflammatory and granulomatous tissues also show extensive FDG uptake, (2) lesions <1 cm in size can often not be detected, and (3) mature teratoma is indistinguishable from normal and necrotic tissue. Studies assessing the clinical role of FDG PET in GCT suggest that the technique has a place as a standard tool in evaluating post chemotherapy seminoma residuals. Whether it also improves the assessment of the risks carried by clinical stage I non-seminoma patients and the early prediction of response to salvage chemotherapy is still under investigation, or at least needs to be confirmed by further trials. In relapsing patients with a mismatch between tumor markers and imaging data, FDG PET appears to be useful whenever salvage surgery is considered, although systematic trials are not yet available.

Pitfalls of positive findings in staging esophageal cancer with F-18-fluorodeoxyglucose positron emission tomography

BACKGROUND

18-F-fluorodeoxyglucose positron emission tomography (FDG-PET) is valuable in staging of esophageal cancer. However, FDG-PET may falsely upstage patients leading to incorrect exclusion from surgical treatment. This study was performed to determine the false-positive rate and possible causes.

METHODS

The rate of false-positive lesions on FDG-PET was documented in 86 out of a group of 98 patients. Lesions were defined as false positive when pathological examination was negative or as absence of tumor activity within 6 months of follow-up. To evaluate the influence of a learning curve on the false-positive rate, the PET scans were revised recently.

RESULTS

False-positive lesions were found in 13 patients (13 of 86; 15%). FDG-PET incorrectly revealed only locoregional node metastases in 5 patients in whom surgery with curative intent was performed. Ten lesions in the other 8 patients were classified as distant organ or as nonregional node metastases (M1a/1b). Finally, 5 patients upstaged to M1a/1b underwent a curative resection. The number of false-positive lesions decreased from 16 to 5 (6%) after revision.

CONCLUSIONS

Proper interpretation of FDG-PET in staging esophageal cancer is impeded by false-positive results. Even after completion of the learning curve, positive FDG-PET findings still have to be confirmed by additional investigations.

Apport de l’imagerie au 18FDG dans la prise en charge du cancer du testicule

The key to prognosis. Initial staging and early recurrence diagnosis are key parameters in the treatment and outcome of testicular cancer. Initial staging. It is difficult using conventional modalities, which can miss node involvement and are non-specific since enlargement does not rhyme with involvement. 18FDG PET improves the accuracy of initial staging. Residual mass and recurrences. Existence of residual mass or enhancement of its Volume in the presence of an otherwise beneficial chemotherapy is difficult to manage. Several studies have demonstrated the value of 18FDG imaging in such cases. As for follow-up whole body 18FDG can prevent multiple diagnostic imaging and can diagnose recurrences with greater diagnostic accuracy than with other imaging modalities.

Positron emission tomography for urological tumours

For urological tumours, positron emission tomography (PET) is currently most useful in testicular cancer. In patients with residual masses or raised marker levels after treatment, PET is both sensitive and specific for detecting recurrent disease, at suspected and unsuspected sites. Although fewer studies are available it also appears to be useful for staging at diagnosis, although this requires further investigation. Prostate cancer imaging has been more variable, with studies showing that PET cannot reliably differentiate between tumour and hypertrophy. It is not as good as a bone scan for defining bone metastases. In renal cancer, PET can be used to define the primary tumour, providing better staging of local recurrence than computed tomography (CT), and to define metastatic disease. There are few studies in bladder cancer, and despite excretion of the tracer via the bladder in early studies, it has better results than CT or magnetic resonance imaging for local staging; again it can detect metastases. Overall, the place of PET in urological tumours is developing, with the strongest areas undoubtedly being testicular and renal cancer. Tracers other than fluorodeoxyglucose are being examined and are providing further information.

Differentiating solitary pulmonary metastases in patients with extrapulmonary neoplasmas using FDG-PET

The purpose of this preliminary study is to evaluate the characteristics of solitary pulmonary lesions in patients using extrapulmonary neoplasmas with 18F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET). Thirty-two patients with extrapulmonary neoplasmas who had solitary pulmonary lesions and were suspected for pulmonary metastasis underwent an oncological survey with FDG-PET. Standard uptake value (SUV) and the ratio of lesion-to-background (L/B ratio) were used as parameters to differentiate and characterize the solitary pulmonary lesions. Using SUV > 2.5 or L/B ratio > 3 as the cutoff to diagnose malignancy, FDG-PET correctly identified 29 true-positive cases. However, FDG-PET failed to interpret two false-positive and one false-negative cases. The accuracy of FDG-PET was 91%. We concluded that FDG-PET is an accurate modality to differentiate solitary pulmonary lesions in patients with extrapulmonary neoplasmas.

Positron emission tomography in cancer research and treatment

Positron emission tomography (PET), the imaging of pharmaceuticals labeled with positron-emitting radionuclides, is a rapidly growing modality for the diagnosis and management of cancer. PET yields high-quality images characterizing substrate metabolism, cellular proliferation, receptor density, and other parameters that can be used to identify cancer and evaluate its response to therapies. The technique mainly utilized in cancer management is FDG-PET, which exploits the abnormal glucose metabolism of cancer cells first characterized by Warburg. We discuss the principles of PET, the currently available instrumentation and radiopharmaceuticals, the efficacy of FDG-PET in the management of cancer, and the prospects for near-term advances in cancer using PET.

Adjuvant chemotherapy for high-risk low-stage germ-cell tumours

PURPOSE OF REVIEW

To review the assessment and management of early germ-cell tumours.

RECENT FINDINGS

A role has evolved for adjuvant chemotherapy in stage I disease postorchidectomy and in the primary management of stage II disease.

SUMMARY

A range of approaches offer high survival in early germ-cell tumours. Treatment should factor in patient choice and resource issues. More sensitive imaging with Positron Emission Tomography may allow more appropriate treatment decisions.

Positron emission tomography in urologic oncology

BACKGROUND

Positron emission tomography (PET) is an emerging imaging modality that is being investigated for use in urologic oncology. PET scanning using the radioactive glucose analog FDG has proven to be a highly accurate imaging test for diagnosing and staging a variety of non-urologic cancer types. This review was performed to determine the role of PET imaging in genitourinary malignancies.

METHODS

A review of the literature focusing on PET and urologic oncology was performed. The role of PET imaging was reviewed in prostate, bladder, renal, and testicular cancer.

RESULTS

In testicular cancer, PET has a higher diagnostic accuracy than computed tomography (CT) for both staging and re-staging and should be the test of choice for the assessment of a CT-visualized residual mass following chemotherapy. In prostate, renal, and bladder cancer, the current role of PET is still being defined, but it has a high positive predictive value and can be used for problem solving in patients with indeterminate findings on conventional imaging. Its role in the diagnosis and staging of prostate cancer is hampered by the generally low glycolytic rate of most prostate tumors and their metastases. It has shown promise for staging and re-staging patients with advanced-stage disease and aggressive tumors suspected by a high tumor grade and high prostate-specific antigen velocity. PET has also demonstrated success when applied to renal cell carcinoma in classifying indeterminate renal masses as well as residual renal fossa masses following nephrectomy, gauging response to therapy, and staging and re-staging patients with a known diagnosis of renal cell carcinoma.

CONCLUSIONS

PET imaging has demonstrated great potential in certain applications, but further investigations are necessary to determine its eventual place as an imaging modality in genitourinary malignancies.

18F-fluoro-2-deoxyglucose-positron emission tomography in the evaluation of nonseminomatous germ cell tumours at relapse

OBJECTIVES

To compare the performance of 18F-fluoro-2-deoxyglucose-positron emission tomography (FDG-PET) and computed tomography (CT) in the follow-up of nonseminomatous germ cell tumours (NSGCT) in the retroperitoneum.

PATIENTS AND METHODS

FDG-PET was used 25 times in 15 patients diagnosed with NSGCT. At the time of diagnosis five patients each were in stage I, II and III. Five patients had pure embryonal carcinoma, two had yolk sac tumours, one choriocarcinoma and seven had mixed tumours.

RESULTS

Eleven patients either presented with retroperitoneal disease or this did not disappear after chemotherapy. The results of both examinations coincided in 18 cases and were contradictory in the other seven, the difference being statistically significant (P=0.042).

CONCLUSION

In these patients FDG-PET detected the retroperitoneal relapse of NSGCT, in advanced stages treated with surgery plus chemotherapy, earlier than did CT; it also detected the presence of mature teratoma in residual retroperitoneal masses more accurately than CT. More extensive trials are needed before making conclusions about FDG-PET imaging as a routine method for NSGCT.

Follow-up surveillance strategies for genitourinary malignancies

BACKGROUND

Genitourinary cancers account for more than 20% of all malignancies in the United States. These cancers do not usually yield rapid mortality, thereby necessitating longer-term surveillance strategies.

METHODS

A review and analysis of relevant studies were performed. Follow-up strategies are proposed to reflect effective methods to detect recurrent prostate, bladder, renal, and testicular cancers. Cost analysis was performed using Medicare reimbursement rates.

RESULTS

For genitourinary tumors, follow-up tests can be planned rationally based on detection rates and patterns. Tumor grade and stage drive follow-up strategies, along with therapeutic implications of detecting a recurrence. Symptomatic recurrences often obviate the need for radiographic tests and can minimize costs. Stage- specific plans for these four urologic malignancies are outlined specifically.

CONCLUSIONS

Not all surveillance approaches have been critically tested for follow-up of genitourinary tumors, but ample data are available to propose sound medical and economic strategies.

Prospective comparison of [18F]fluorodeoxyglucose positron emission tomography with conventional assessment by computed tomography scans and serum tumor markers for the evaluation of residual masses in patients with nonseminomatous germ cell carcinoma

BACKGROUND

To assess the ability of [(18)F]fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET) to predict the viability of residual masses after chemotherapy in patients with metastatic nonseminomatous germ cell tumors (GCT), PET results were compared in a blinded analysis with computed tomography (CT) scans and serum tumor marker changes (TUM) as established methods of assessment.

METHODS

Independent reviewers who were blinded to each other's results evaluated the PET results and corresponding CT scan and TUM results in 85 residual lesions from 45 patients. All patients were treated within prospective clinical trials and received primary/salvage, high-dose chemotherapy with autologous blood stem cell support for primary poor prognosis disease or recurrent disease. PET results were assessed both visually and by quantifying glucose uptake (standardized uptake values). Results were validated either by histologic examination of a resected mass and/or biopsy (n = 28 lesions) or by a 6-month clinical follow-up after evaluation (n = 57 lesions).

RESULTS

F-18 FDG PET showed increased tracer uptake in 32 of 85 residual lesions, with 29 true positive (TP) lesions and three false positive (FP) lesions. Fifty-three lesions were classified by PET as negative (no viable GCT), 33 lesions were classified by PET as true negative (TN), and 20 lesions were classified by PET as false negative (FN). In the blinded reading of the corresponding CT scan and TUM results, 38 residual lesions were assessed correctly as containing viable carcinoma and/or teratoma. Forty-six lesions were classified as non-suspicious by CT scan/TUM (33 TN lesions and 14 falsely classified lesions). PET correctly predicted the presence of viable carcinoma in 5 of these 14 and the absence of viable carcinoma in 3 of these 14 lesions. Resulting sensitivities and specificities for the prediction of residual mass viability were as follows: PET, 59% sensitivity and 92% specificity; radiologic monitoring, 55% sensitivity and 86% specificity; and TUM, 42% sensitivity and 100% specificity. The positive and negative predictive values for PET were 91% and 62%, respectively. The diagnostic efficacy of PET did not improve when patients with teratomatous elements in the primary tumor were excluded from the analysis. In patients with multiple residual masses, a uniformly increased residual F-18 FDG uptake in all lesions was a strong predictor for the presence of viable carcinoma.

CONCLUSIONS

F-18 FDG PET imaging performed in conjunction with conventional staging methods offers additional information for the prediction of residual mass histology in patients with nonseminomatous GCT. A positive PET is highly predictive for the presence of viable carcinoma. Other useful indications for a PET examination include patients with multiple residual masses and patients with marker negative disease.

PET and PLAP in suspected testicular cancer relapse: beware sarcoidosis

A 31-year-old man previously treated with chemotherapy for metastatic testicular cancer presented with new mediastinal lymphadenopathy and peripheral lung opacities. Serum tumour markers were not elevated and a PET (positron emission tomography) scan revealed increased FDG (fluoro-deoxyglucose) uptake in the lungs and mediastinum consistent with testis cancer relapse. A biopsy of a mediastinal lymph node was performed and the pathology was that of sarcoidosis. Immunohistochemistry however was positive for PLAP (placental alkaline phosphatase) and negative for EMA (epithelial membrane antigen). This immunohistochemical profile raised concerns that the observed pathology represented a sarcoid reaction to micro-metastatic testicular cancer relapse. We performed immunohistochemical pathology analysis on four known cases of sarcoidosis and found the same immunohistochemical-staining pattern. This case highlights the problem of specificity when interpreting the significance of PET scans and immunohistochemical analysis in this situation. Sarcoidosis, a condition that has been associated with testicular cancer, should always be considered in the differential diagnosis.

Positron emission tomography in urological malignancy

Positron emission tomography is a unique imaging modality with the capability of studying regional metabolism. The major clinical applications of positron emission tomography have been in the detection of brain, breast, cardiac, lung and colorectal tumours, as well as the evaluation of coronary artery disease by imaging the metabolism of heart muscle. In the field of urology, positron emission tomography has been evaluated in the relevant malignancies with promising results in certain areas and disappointing results in others. This article attempts to summarize recent advances in positron emission tomography scanning with regards to urological malignancy. At this stage positron emission tomography scanning is capable of visualizing urological tumours and associated lymph nodes and distal metastatic sites. However, its use is severely limited by the excretion of the most commonly used radioisotope via the urinary tract, making pelvic imaging particularly unrewarding. It is, however, undoubtedly capable of diagnosing malignancy in soft tissue masses or lymph nodes before these changes become apparent on conventional cross-sectional imaging modalities (computerized tomography or magnetic resonance imaging). Larger studies are required before it can be advocated for clinical use in the field of urology.