Incidental Focal (18)F-FDG Uptake in the Prostate: Clinical Significance and Differential Diagnostic Criteria

Applicability and performance of 18F-FDG PET-based modalities for whole-body cancer screening: a systematic review and meta-analysis

PURPOSE

Screening tests are the cornerstone for early detection and optimal management of cancers. Most of the present cancer-screening tests are intrusive, time-consuming, and specifically target a particular anatomical site or cancer type. Only a few studies have reported the objective measures of 18F-FDG PET-based cancer screening in asymptomatic individuals. This review and meta-analysis is an attempt to assess the applicability and performance of 18F-FDG PET-based modalities for whole-body cancer screening.

MATERIALS AND METHODS

The systematic review and meta-analysis were performed following PRISMA guidelines. Literature searches in PubMed, Scopus, and Embase were conducted using relevant MeSH terms and keywords, for articles published in the last 2 decades (2000-2022). Pooled estimates of diagnostic test accuracy-including sensitivity, specificity, positive-likelihood ratio, negative-likelihood ratio, and hierarchical summary ROC (HSROC) curve were generated using bivariate random-effects meta-analysis.

RESULTS

Seventeen studies were included in the systematic review and 13 studies were deemed eligible for meta-analysis. The mean estimates of pooled sensitivity, specificity, positive-likelihood ratio, negative-likelihood ratio, and Odds ratio using 18F-FDG PET with a 95% confidence interval were 0.47 (0.25-0.69), 0.97 (0.95-0.98), 18.8 (6.8-51.5), 0.45 (0.27-0.76), 41.0 (7.9-211.8) and for 18F-FDG PET/CT were 0.83 (0.75-0.88), 0.98 (0.97-0.99), 49.7 (29.2-84.5), 0.15 (0.8-0.28), 329.9 (125.0-870.8), respectively. Among screening modalities, 18F-FDG PET/CT had a higher accuracy i.e., the area under the HSROC curve (AUC): 0.91 (0.87-0.95) compared to 18F-FDG PET: 0.72 (0.61-0.82).

CONCLUSION

This study demonstrates that currently 18F-FDG PET-based screening has limited applicability for population-based cancer-screening programs. However, it has a promising role as a combined screening strategy for at-risk individuals and allows for comprehensive diagnostic and prognostic evaluation in high-resource settings.

Definitions of Incidental [18F]FDG PET/CT Findings in the Literature: A Systematic Review and Definition Proposal

Objectives: The objectives of this study were (1) to systematically review the currently used definitions of incidental 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography findings (IPFs) in the literature and (2) to propose an IPF definition. Methods: A systematic search was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The search was guided by the question "How is IPF defined?" and was performed in MEDLINE, Embase, and the Cochrane Library. The retrieved studies were reviewed and analyzed. The definitions of IPFs in the included studies were compiled into two sets of categories based on the description of FDG uptake and the specification of clinical factors in defining IPFs. Results: The systematic literature search identified 4852 publications accessible for title-abstract screening, which yielded 395 studies for full-text assessment. Sixty-five studies met the eligibility criteria and were included. Sixty-two percent mentioned "FDG uptake" in their definition. In 40% of the definitions, "Focal FDG uptake" was specified, while "FDG uptake in the surrounding tissue" was included in 15%. Fifty-seven percent stated that IPFs were "Unrelated to PET/CT indication". Thirty-four percent specified IPFs as "Present in other organ than PET/CT indication", whereas 20% included "No known disease related to IPF". Seventeen percent of the definitions comprised a "New finding", while 15% and 11% encompassed a "Clinical asymptomatic patient" and "Not a metastasis", respectively. Finally, 5% of the definitions included "Potential clinical significance". Conclusions: No generally accepted definition of IPFs currently exists. We propose an IPF definition based on explicit FDG uptake and clinical patient-related factors.

Unexpected focal fluorodeoxyglucose uptake in main organs; pass through or pass by?

Since the inception of fluorine-18 fluorodeoxyglucose (F-18 FDG), positron emission tomography/computed tomography (PET/CT) utilizing F-18 FDG has become widely accepted as a valuable imaging modality in the field of oncology, with global prevalence in clinical practice. Given that a single Torso PET/CT scan encompasses the anatomical region from the skull base to the upper thigh, the detection of incidental abnormal focal hypermetabolism in areas of limited clinical interest is both feasible and not uncommon. Numerous investigations have been undertaken to delineate the distinctive features of these findings, yet the outcomes have proven inconclusive. The incongruent results of these studies present a challenge for physicians, leaving them uncertain about the appropriate course of action. This article provides a succinct overview of the characteristics of fluorodeoxyglucose, followed by a comprehensive discussion of the imaging findings and clinical significance associated with incidental focal abnormal F-18 FDG activity in several representative organs. In conclusion, while the prevalence of unrecognized malignancy varies across organs, malignancies account for a substantial proportion, ranging from approximately one-third to over half, of incidental focal uptake. In light of these rates, physicians are urged to exercise vigilance in not disregarding unexpected uptake, facilitating more assured clinical decisions, and advocating for further active evaluation.

Clinical Value of Surveillance 18F-fluorodeoxyglucose PET/CT for Detecting Unsuspected Recurrence or Second Primary Cancer in Non-Small Cell Lung Cancer after Curative Therapy

Simple Summary

Non-small cell lung cancer (NSCLC) patients are at considerable risk of recurrence or second primary cancer (SPC) after curative therapy. The utility of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) surveillance to detect recurrent lesions in NSCLC patients without suspicion of recurrence has not been established. The aim of our retrospective study was to evaluate the diagnostic value of surveillance FDG PET/CT for detecting clinically unsuspected recurrence or SPC in patients with NSCLC after curative therapy. In a cohort of 2684 NSCLC patients after curative therapy, surveillance FDG PET/CT showed good diagnostic efficacy for detecting clinically unexpected recurrence or SPC. Furthermore, the diagnostic performance was improved in subgroups of patients with advanced stage prior to curative therapy, PET/CT scans performed within 3 years after curative-intent therapy, and curative surgery. Surveillance PET/CT can be more useful when performed soon after therapy in curative surgery recipients and those with an advanced disease stage considering its diagnostic efficacy and yield.

Abstract

We evaluated the diagnostic value of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT surveillance for detecting clinically unsuspected recurrence or second primary cancer (SPC) in patients with non-small cell lung cancer (NSCLC) after curative therapy. A total of 4478 surveillance FDG PET/CT scans from 2864 NSCLC patients without suspicion of recurrence after curative therapy were reviewed retrospectively. In 274 of 2864 (9.6%) patients, recurrent NSCLC or SPC was found by surveillance PET/CT during clinical follow-up. Surveillance PET/CT scans showed sensitivity of 98.9% (274/277), specificity of 98.1% (4122/4201), accuracy of 98.2% (4396/4478), positive predictive value (PPV) of 77.6% (274/353), and negative predictive value of 99.9% (4122/4125). The specificity and accuracy in the curative surgery group were significantly higher than those in the curative radiotherapy group. PPV was significantly improved in subgroups of patients with advanced stage prior to curative therapy, PET/CT scans performed within 3 years after curative-intent therapy, and curative surgery. FDG PET/CT surveillance showed good diagnostic efficacy for detecting clinically unexpected recurrence or SPC in NSCLC patients after curative therapy. It can be more useful when performed soon after therapy in curative surgery recipients and those with an advanced disease stage considering its diagnostic efficacy and yield.

Prostate incidentaloma on 18F-fluorodeoxyglucose positron emission tomography: Diagnostic value of volumetric positron emission tomography parameters

OBJECTIVE

To evaluate whether volumetric PET parameters such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG) contributed to maximum standardized uptake value (SUVmax) in predicting prostate carcinoma in the prostate incidentalomas (PI) in 18F-FDG PET/CT.

MATERIALS AND METHODS

This retrospective study comprised 107 patients with PI of 4723 male patients who had undergone 18F-FDG PET/CT. SUVmax and volumetric PET parameters of PIs were assessed. MTV and TLG were acquired with each SUV threshold as 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0.

RESULTS

The PI incidence was 2.3%, and the malignancy ratio of PI was 15.9%. According to further analysis results, 17 patients were in the malignant group, and 46 patients were in the benign group. Malignant PIs had higher SUVmax (10.6 vs. 6.4 and p<0.01), MTV (all p < 0.01) and TLG (all p < 0.01) than benign incidentalomas. All volumetric PET parameters had higher area under the curve (AUC) than SUVmax. SUVmax AUC was 0.835 [95% confidence interval (CI): 0.728-0.942]. MTV 2.5 and TLG 2.5 had the highest performance for predicting malignant PI.MTV2.5 AUC was 0.871 (95% CI: 0.775-0.968), and TLG2.5 AUC was 0.882 (95% CI: 0.797-0.967). Using TLG 2.5 greater than 29.8 as the cut-off point, the sensitivity and specificity for malignancy prediction were 94.1% and 82.6%, respectively.

CONCLUSION

In this study, in which the effectiveness of volumetric parameters in the diagnosis of PI was evaluated for the first time, it was shown that they could potentially have clinical value along with SUVmax.

Seminal Vesicle Urinary Reflux After TURP Mimicking Vesicular Invasion From Prostate Cancer on 18F-Choline PET/CT

Seminal vesicles are paired secretory glands located posterior to the bladder in men that produce seminal fluid to maintain sperm. Seminal vesicle reflux into the prostatic ducts may be associated with prostatitis in older patients or may represent a very rare complication of transurethral prostate resection in patients with prostatic cancer. This condition is frequently accidentally diagnosed on excretory urography and/or retrograde urethrogram. Clinical presentation includes pain, fever, recurrent epididymitis-prostatitis, and post void dribbling.

Incidentalomas of the prostate detected by 18-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography

INTRODUCTION

Prostate incidentalomas are prostatic lesions suspicious for cancer discovered by imaging patients without a known history of prostatic cancer (PCa) for other reasons. 18-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG PET) is used to diagnose, stage, and assess response to treatment for numerous cancers, but it is not routinely used for PCa. We aimed to determine the rate of detection of prostate incidentalomas in patients undergoing FDG PET and to evaluate the natural history of these lesions.

METHODS

A retrospective review was conducted of all FDG PET scans performed between 2005 and 2017 at a single institution. Patients were selected who had prostatic uptake without a history of PCa. Clinical data were collected from electronic medical records to determine how the prostate incidentalomas were further evaluated and to define the rate of malignancy.

RESULTS

A prostate incidentaloma was identified in 309 (1.0%) of 31 019 FDG PET scans performed on men. A prostate-specific antigen (PSA) test was obtained in 40.1% of patients within six months of prostate incidentaloma detection. Six patients underwent a multiparametric magnetic resonance imaging (mpMRI) of the prostate, which identified PCa in one case. Overall, PCa was diagnosed in 33 cases, representing 10.7% of the prostate incidentalomas and 0.1% of the scanned patients. PCa was intermediate- or high-risk in 27 (8.7%) of the prostate incidentalomas.

CONCLUSIONS

Incidental lesions detected in the prostate by FDG PET may represent clinically significant PCa. Referral to a urologist for further evaluation should be considered if the patient is otherwise in reasonable health.

Case: Incidental 18F-fluorodeoxyglucose-positron emission tomography/computed tomography prostate uptake: How should these patients be managed?

18F-fluorodeoxyglucose-positron emission tomography/ computed tomography (18F-FDG PET/CT) is a widely used diagnostic tool for whole-body imaging, and incidental prostatic uptake occurs in approximately 1% of patients undergoing the exam. Is 18F-FDG PET/CT a reliable screening tool for prostate cancer? Should these patients undergo transrectal ultrasound (TRUS)-guided prostate biopsies? Studies have indicated that 18F-FDG PET/CT has a low positive predictive value for prostate cancer and is not recommended for screening;1 however, other studies suggest that when a discrete focal 18F-FDG uptake is discovered without coincidental calcification, particularly in the peripheral zone of the prostate, further clinical evaluation is recommended. We present two patients with incidental 18F-FDG PET/CT prostatic uptake who were found to have high-grade prostate cancer. Although 18F-FDG PET/CT has not been determined to be a reliable screening tool for prostate cancer, patients with incidental 18F-FDG uptake in the prostate should be referred for urological evaluation.

Clinical Significance of Incidental Focal 18F-FDG Uptake in the Spinal Cord of Patients with Cancer

PURPOSE

We investigated the incidence, location, and clinical significance of focal ¹⁸F-FDG uptake of the spinal cord in patients with cancer.

METHODS

We reviewed the medical records of 22,937 consecutive adult patients with known or suspicious malignancy who underwent ¹⁸F-FDG PET/CT. PET/CT scans with incidental focal spinal cord uptake were selected and retrospectively reviewed to determine the presence, location, number, and maximum standardized uptake value (SUV_max) of any focal hypermetabolic lesions of the spinal cord. In subjects with focal spinal uptake, clinical characteristics and clinical follow-up results, including follow-up PET/CT, were reviewed.

RESULTS

Incidental focal spinal cord uptake was observed in 69 of 22,937 adult patients (incidence = 0.3%; M:F = 31:38; age, 55.8 ± 14.7 years). Seventy-eight focal hypermetabolic lesions on spinal cord in the PET/CT scans of the 69 study subjects were analyzed. The most common sites of focal spinal cord uptake were the T12 vertebra (47/78; 60.3%) and L1 vertebra (20/78; 25.6%). Multifocal cord uptake was found in 8 of 69 patients (11.6%). The average SUV_max for cord uptake was 2.5 ± 0.5 (range, 1.4∼3.9). There was no clinical or imaging evidence of abnormalities in the spinal cord, both at the time of PET/CT and during clinical follow-up.

CONCLUSIONS

Although incidental focal ¹⁸F-FDG uptake of the spinal cord is rare in patients with cancer, it may be physiological or benign, but it should not be considered as malignant involvement. Common sites for the uptake were in the T12 and L1 spine levels.

Does focal incidental 18F-FDG PET/CT uptake in the prostate have significance?

PURPOSE

(18)F-FDG PET/CT is used to characterize many malignancies, but is not recommended for localized prostate cancer. This study explores the value of multi-parametric MRI (mpMRI) in characterizing incidental prostate (18)F-FDG uptake.

METHODS

Thirty-one patients who underwent (18)F-FDG PET/CT for reasons unrelated to prostate cancer and prostate mpMRI were eligible for this retrospective study. The mpMRI included T2-weighted (T2W), dynamic contrast enhancement (DCE), apparent diffusion coefficient (ADC), and MR spectroscopy (MRS) sequences. Fourteen patients were excluded (n = 8 insufficient histopathology, n = 6 radical prostatectomy before PET), and final analysis included 17 patients. A nuclear medicine physician, blinded to clinicopathologic findings, identified suspicious areas and maximum standardized uptake values (SUV max) on (18)F-FDG PET/CT. Sector-based imaging findings were correlated with annotated histopathology from whole-mount or MRI/transrectal ultrasound fusion biopsy samples. Positive predictive values (PPVs) were estimated using generalized estimating equations with logit link. Results were evaluated with Kruskal-Wallis and Dunn's multiple comparisons tests.

RESULTS

The PPV of (18)F-FDG PET alone in detecting prostate cancer was 0.65. Combining (18)F-FDG PET as a base parameter with mpMRI (T2W, DCE, ADC, and MRS) increased the PPV to 0.82, 0.83, 0.83, and 0.94, respectively. All benign lesions had SUV max < 6. Malignant lesions had higher SUV max values that correlated with Gleason scores. There was a significant difference in SUV max per prostate between the Gleason ≥ 4 + 5 and benign categories (p = 0.03).

CONCLUSIONS

Focal incidental prostate (18)F-FDG uptake has low clinical utility alone, but regions of uptake may harbor high-grade prostate cancer, especially if SUV max > 6. Using mpMRI to further evaluate incidental (18)F-FDG uptake aids the diagnosis of prostate cancer.

Clinical Significance of Incidental 18F-FDG Uptake in the Pyriform Sinus Detected by PET/CT

PURPOSE

We investigated the significance of unexpected focal pyriform sinus FDG uptake and determined the ability of PET/CT parameters to identify malignancy.

MATERIALS AND METHODS

FDG PET/CT reports of 56,585 consecutive subjects were retrospectively reviewed, and 281 cases (0.50%) with focal pyriform sinus uptake were included. PET images were assessed for maximum standardized uptake values (SUVmax) and asymmetric indices of FDG activity, and CT images were evaluated for pyriform sinus narrowing. The final diagnosis was determined by tissue biopsy, laryngoscopy, radiological findings, and clinical follow-up.

RESULTS

Among the 281 subjects, final diagnosis was pyriform sinus malignancy in 29 (10.3%) and benignity in 215 cases (76.5%). Malignant lesions had significantly higher SUVmax (9.13 ± 3.64 vs. 3.53 ± 1.01) and asymmetric index (4.16 ± 1.81 vs. 1.54 ± 0.39) compared to benign causes. Patients with malignant lesions also had higher cervical lymph node SUVmax (6.66 ± 8.79 vs. 2.76 ± 2.46, all P < 0.001). Lesion SUVmax ≥4.24 identified malignancy with a sensitivity of 93.1% and specificity of 86.5%. Asymmetric index ≥1.81 had a sensitivity of 100% and specificity of 89.7%.

CONCLUSION

Incidentally identified focal pyriform sinus uptake on FDG PET/CT should be evaluated for possible malignancy in the presence of high SUVmax or asymmetric index.

Retrospektive Analyse von Zufallsbefunden, die bei Patienten mit kutanem malignen Malignom durch (18) F-Fluordeoxyglucose-PET/CT erhoben wurden

HINTERGRUND UND ZIELE

Bei der (18) F-Fluordeoxyglucose-Positronenemissionstomographie/Computertomographie (FDG-PET/CT) ergeben sich häufig Zufallsbefunde. In der vorliegenden Studie konzentrierten wir uns auf mittels FDG-PET/CT erhaltene Zufallsbefunde bei Patienten mit kutanem Melanom und überprüften deren Relevanz hinsichtlich weiterer diagnostischer Maßnahmen und Interventionen.

PATIENTEN UND METHODEN

Die Krankenakten von 181 konsekutiven Melanom-Patienten wurden retrospektiv ausgewertet, um das Management von Zufallsbefunden zu dokumentieren. Der Schwerpunkt lag dabei auf den histologischen Befunden.

ERGEBNISSE

Bei 33 von 181 (18 %) Patienten lagen 39 relevante Zufallsbefunde vor, und zwar im Kolorektalbereich (n = 15 Patienten), in der Schilddrüse (n = 8), der Prostata (n = 2), dem Bewegungsapparat (n = 2), in Lymphknoten (n = 2), der Parotis (n = 1), den Mandeln (n = 1), den Nieren (n = 1) und der Gallenblase (n = 1). Bei 25 Patienten schlossen sich weitere diagnostische Verfahren an, wobei in 21 Fällen ein klinisches Korrelat nachgewiesen wurde. Bei 16 von 21 Patienten ergab sich eine Neoplasie, darunter fünf maligne Läsionen (vier Kolonkarzinome und ein Prostatakarzinom). Die Malignome wurden frühzeitig diagnostiziert und in der Mehrzahl der Fälle erfolgreich entfernt.

SCHLUSSFOLGERUNGEN

Der Einsatz der FDG-PET/CT als Routine-Diagnostik wird in den Leitlinien empfohlen und ist indiziert bei malignem Melanom ab Stadium IIC. In dieser Studie wurden auf effektive Weise ansonsten nicht erkannte Krebserkrankungen, insbesondere Kolonkarzinome, detektiert. In den meisten Fällen war eine frühe Intervention möglich. Zufallsbefunde durch FDG-PET/CT sollten, unter Berücksichtigung des Zustands und der Wünsche des Patienten, mit den geeigneten diagnostischen Maßnahmen abgeklärt werden.

Clinical Relevance of Incidental Prostatic Lesions on FDG-Positron Emission Tomography/Computerized Tomography-Should Patients Receive Further Evaluation?

PURPOSE

FDG ((18)F-fluoro-2-deoxy-D-glucose)-PET/CT (positron emission tomography)/(computerized tomography) is a widely used diagnostic tool for whole body imaging. Incidental prostatic uptake is often found on FDG-PET/CT. The objective of this study was to determine the clinical relevance of incidental prostatic uptake on FDG-PET/CT.

MATERIALS AND METHODS

We analyzed 108 consecutive male patients with bladder cancer who underwent FDG-PET/CT and subsequently radical cystoprostatectomy between May 2009 and November 2014. PET/CT scans were blindly reviewed by a dedicated nuclear medicine physician for incidental prostatic FDG uptake. If present, the maximum standardized uptake value was determined. Subsequently incidental prostatic uptake was categorized as suspect, indeterminate or nonsuspect for prostate cancer.

RESULTS

Incidental prostatic uptake was present in 43 of 108 patients (40%). Of these 43 patients 13 (30%) had occult prostate cancer in cystoprostatectomy specimens. Overall prostate cancer was found in 25 of 108 specimens (23%). If all incidental prostatic uptake was regarded as prostate cancer, the sensitivity and specificity of FDG-PET/CT for prostate cancer detection were 52% and 64%, respectively. Positive and negative predictive values were 30% and 82%, respectively. If only lesions labeled suspect or indeterminate were regarded as prostate cancer, sensitivity, specificity, and positive and negative predictive values were 32%, 76%, 29% and 79%, respectively. Categorizing indeterminate lesions as nonprostate cancer did not improve diagnostic accuracy. Gleason score did not correlate with maximum standardized uptake value or serum prostate specific antigen.

CONCLUSIONS

Incidental prostatic uptake on FDG-PET/CT has a low positive predictive value for prostate cancer. An attempt to classify lesions as suspect or nonsuspect did not increase diagnostic accuracy. Based on these results physicians should be cautious about applying invasive diagnostic methods to detect prostate cancer in case of incidental prostatic uptake on FDG-PET/CT.

Clinical significance of incidental FDG uptake in the prostate gland detected by PET/CT

The value of FDG-positron emission tomography/computed tomography (PET/CT) for detecting prostate cancer is unknown. We aimed to investigate the clinical value of incidental prostate FDG uptake on PET/CT scans. We reviewed 6128 male patients who underwent FDG-PET/CT scans and selected cases that reported hypermetabolic lesion in the prostate. The patients who have prior history of prostate carcinoma or prostate surgery were excluded from the study. We have analyzed the correlation between PET/CT findings and serum prostate-specific antigen (PSA) levels, imaging (USG), urological examinations and biopsy. Incidental 18F-FDG uptake of the prostate gland was observed in 79 patients (1.3%). While sixteen of them were excluded due to inadequate clinical data, the remaining 63 patients were included for further analysis. The patients were divided into two groups; 8 patients (12.7%) in the malignant group and 55 patients (87.3%) in the benign group. The SUVmax values were not significantly different between the two groups. In 6 (75%) patients with prostate cancer, FDG uptake was observed focally in the peripheral zone of the prostate glands. There was no significant correlation between the SUVmax and the PSA levels. Incidental 18F-FDG uptake in the prostate gland is a rare condition, but a substantial portion of it is associated with the cancer. Benign and malignant lesions of the prostate gland in FDG-PET/CT imaging could not be reliably distinguished. The peripheral focally FDG uptake of prostate glands should be further examined with the clinical and labaratory evaluations.

Multicentre study of 18F-FDG-PET/CT prostate incidental uptake

AIM

The purpose of our study was to establish the prevalence and pathological nature of fluorine-18-fluorodeoxyglucose (18F-FDG) prostate incidental uptake (PIU) among patients studied for non-prostate-malignant purposes in three nuclear medicine centres.

METHODS

We retrospectively evaluated 20,422 scans performed on male patients; all patients underwent 18F-FDG-PET/CT for purposes not related to prostate disease.

RESULTS

Among 20,422 patients PIU was identified for 280 (1.4 %) with an average age of 70 ± 10.7 years. Sixty-three of the 280 patients with PIU (22.5 %) underwent PSA dosage and biopsy to determine the nature of the incidental uptake. Thirty-five of the 63 (55.5 %) PIU were malignant whereas 28/63 (44.5 %) were benign. The average value of PSA for patients with benign PIU was 3.7 ± 2.8 ng/ml whereas it was 7.8 ± 8.2 ng/ml in patients with malignant PIU; this difference was statistically significant. For malignant lesions, the average lesion-to-liver SUVmax ratio was 2.9 ± 2.5 and the average lesion-to-blood-pool SUVmax ratio was 3.7 ± 2.5. For benign lesions, the average lesion-to-liver SUVmax ratio was 2.5 ± 1.7 and the average lesion-to-blood-pool SUVmax ratio was 3.5 ± 2.4; there was no statistically significant difference between lesion-to-liver and lesion-to-blood-pool SUVmax ratios for benign and malignant lesions.

CONCLUSION

Because PIU values are indicative of malignancy for a substantial percentage of patients, further investigation is required.

Incidental uptake of 18F-fluorodeoxyglucose in the prostate gland. Systematic review and meta-analysis on prevalence and risk of malignancy

AIM

To perform a systematic review and meta-analysis of published data on the prevalence and risk of malignancy of prostatic incidental uptake (PIU) detected by fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) or PET/computed tomography (PET/CT).

PATIENTS, MATERIAL, METHODS

A comprehensive literature search of studies published up to February 2014 was performed. Pooled prevalence and malignancy risk of PIU were calculated on a per patient-based analysis including 95% confidence interval (95%CI). Furthermore, we assessed some parameters as potential predictors of malignant PIU.

RESULTS

Six studies including 47925 patients who underwent 18F-FDG PET/CT were selected. Pooled prevalence of PIU was 1.8% (95%CI: 1.3-2.3%). Overall, 444 patients with PIU were further evaluated and 121 underwent biopsy. The pooled risk of malignancy in patients with PIU further evaluated or verified by biopsy were 17% (95%CI: 12-23%) and 62% (95%CI: 54-71%), respectively. A higher mean age was observed in the group of malignant PIUs compared to benign PIUs. There was a trend towards a higher mean SUV(max) in the group of malignant PIUs but without a statistically significant difference compared to benign PIUs. Peripheric site of PIU but not presence or absence of calcification was a predictor of malignancy.

CONCLUSIONS

PIU is observed in about 1.8% of 18F-FDG PET/CT scans performed in male patients carrying a significant risk of malignancy. Therefore, whenever a PIU is detected further investigation is warranted to exclude malignancy, in particular when PIU is located in the peripheric site of prostate gland.

Incidental prostate ¹⁸F-FDG uptake without calcification indicates the possibility of prostate cancer

Incidental ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake in the prostate is often experienced in clinical practice; however, it is difficult to determine whether incidental uptake is indicative of a malignancy or benign state based on the maximum standardized uptake value (SUVmax). In the present study, we investigated the clinical significance of incidental prostate uptake by ¹⁸F-FDG positron emission tomography (PET)/CT, and examined the differences between malignant and benign uptake from a clinicopathological viewpoint. We reviewed 3,236 male subjects who underwent ¹⁸F-FDG PET/CT scans at Hirosaki University Hospital (Japan) from 2008 to 2012 in order to identify cases of incidental prostate FDG uptake. The final diagnosis was made by serum prostate-specific antigen (PSA) levels, biopsy, imaging studies and clinical follow-up with PET findings. Incidental FDG uptake of the prostate was observed in 53 cases (2%). Four cases were excluded due to insufficient clinical data, and 49 cases were included in the present study. Of the 49 cases, 8 (16%) had prostate cancer, while 41 (84%) were benign. All 8 malignant cases had high uptake areas, e.g. in the prostate peripheral zone, where there was no coexistence of calcification or FDG uptake. Of the 41 benign cases, 19 had high uptake in the inner zone, 17 in the peripheral zone, and 5 in both the inner and peripheral zones. Of the 41 cases, 18 (44%) showed FDG uptake coexisting with prostatic calcification. Incidental prostate ¹⁸F-FDG uptake infrequently signifies prostate cancer; however, FDG uptake not coexisting with calcification indicates the possibility of prostate cancer and should be included in the differential diagnosis for performing other clinical examinations.