BCG-induced granulomatous prostatitis—an incidental finding on FDG PET-CT

Granulomatous prostatitis following Bacillus Calmette-Guérin therapy

Granulomatous prostatitis (GP) is a rare form of chronic prostatitis with reported incidence of 0.65-1.5%. Radiological features of GP overlap with those of prostate adenocarcinoma. The following magnetic resonance imaging characteristics can suggest the diagnosis in an appropriate clinical setting: Diffuse or focal nodular low T2 signal, high signal on diffusion-weighted imaging with corresponding low apparent diffusion coefficient signal, and post-contrast imaging with lesion enhancement or rim-enhancing in the setting of caseous necrosis or abscess formation. Even with suspicion on imaging, the overlapping imaging features with prostate adenocarcinoma necessitate biopsy for confirmatory diagnosis. Here, we report a case of a 70-year-old man with GP in the setting of prior intravesicle bacillus Calmette-Guérin administration.

Granulomatous prostatitis after bacille Calmette-Guérin instillation resembles prostate carcinoma: A case report and review of the literature

BACKGROUND

Bacille Calmette-Guérin (BCG) instillation is recommended in patients with non-muscle-invasive bladder cancer who have intermediate-risk and high-risk tumors. However, granulomatous prostatitis is a rare complication induced by BCG instillation, which can easily be misdiagnosed as prostate cancer. Here, we report a case of granulomatous prostatitis that resembled prostate cancer.

CASE SUMMARY

A 64-year-old Chinese man with bladder cancer received BCG instillation. Three days later, he stopped BCG instillation and received anti-infective therapy due to the urinary tract infection. Three months after BCG restart, he had rising total prostate-specific antigen (PSA) (9.14 ng/mL) and decreasing free PSA/total PSA (0.09). T2-weighted images of magnetic resonance imaging (MRI) showed a 28 mm × 20 mm diffuse low signal abnormality in the right peripheral zone, which was markedly hyperintense on high b-value diffusion-weighted MRI and hypointense on apparent diffusion coefficient map images. Considering Prostate Imaging Reporting and Data System score of 5 and possibility of prostate cancer, a prostate biopsy was conducted. Histopathology showed typical features of granulomatous prostatitis. The nucleic acid test for tuberculosis was positive. He was finally diagnosed with BCG-induced granulomatous prostatitis. Thereafter, he stopped BCG instillation and received anti-tuberculosis treatment. During 10 mo follow-up, he had no evidence of tumor recurrence or symptoms of tuberculosis.

CONCLUSION

Temporarily elevated PSA and high followed by low signal abnormality on diffusion-weighted MRI are important indicators of BCG-induced granulomatous prostatitis.

Concurrent Diffuse Pyelonephritis and Prostatitis: Discordant Findings on Sequential FDG PET/CT and 67Ga SPECT/CT Imaging

A 45-year-old man underwent FDG PET/CT for initial imaging evaluation of recurrent Escherichia coli urinary tract infections, which demonstrated no significant FDG uptake in either kidney and subtle FDG uptake in the right prostate lobe. Subsequent Ga SPECT/CT demonstrated abnormal intense gallium uptake throughout the right kidney and entire prostate gland, clearly discordant with PET/CT findings and consistent with unexpected concurrent pyelonephritis and prostatitis. Although FDG has effectively replaced Ga in everyday clinical practice, the current case serves as a reminder that there is still a role for Ga in the evaluation of genitourinary infections.

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.

Granulomatous Prostatitis After Intravesical Bacillus Calmette-Guérin Instillation Therapy: A Potential Cause of Incidental F-18 FDG Uptake in the Prostate Gland on F-18 FDG PET/CT in Patients with Bladder Cancer

PURPOSE

This study aimed to evaluate the possibility that Bacillus Calmette-Guérin (BCG)-induced granulomatous prostatitis can be a potential cause of benign F-18 FDG uptake.

METHODS

A total of 395 bladder cancer patients who underwent F-18 FDG PET/CT (PET/CT) were retrospectively evaluated. Patients were divided into two groups according to BCG therapy status. Elapsed time after BCG therapy, serum PSA level, results of prostate biopsy, and the SUVmax and uptake pattern in the prostate gland were reviewed. For patients who underwent follow-up PET/CT, the changes in SUVmax were calculated.

RESULTS

While 35 % of patients showed prostate uptake in the BCG therapy group, only 1 % showed prostate uptake in the non-BCG therapy group (p < 0.001). Among 49 patients with FDG-avid prostate lesions, none had suspected malignancy during the follow-up period (median: 16 months). Five patients revealed granulomatous prostatitis on biopsy. The incidence of FDG-avid prostate lesions was significantly higher if the elapsed time after BCG therapy was less than 1 year compared to more than 1 year (p < 0.001). Serum PSA was normal in 88 % of patients. All patients with incidental F-18 FDG uptake in the prostate gland showed focal or multifocal prostate uptake, and median SUVmax was 4.7. In 16 patients who underwent follow-up PET/CT, SUVmax was decreased in 14 patients (88 %) without treatment, and no patients demonstrated further increased prostate uptake (p < 0.001).

CONCLUSIONS

BCG-induced granulomatous prostatitis can be a potential cause of benign F-18 FDG uptake, especially in those with a history of bladder cancer treated with BCG. In BCG-induced granulomatous prostatitis, focal or multifocal prostate uptake is frequently seen within 1 year after BCG therapy, and the intensity of prostate uptake is decreased on the follow-up PET/CT without any treatment.

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.

Prevalence and risk of cancer of incidental uptake in prostate identified by fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography

OBJECTIVE

The objective was to investigate the prevalence of incidental fluorine-18 fluorodeoxyglucose (FDG) uptake in positron emission tomography/computed tomography.

METHODS

A total of 11,239 male nonprostate disease patients were included retrospectively.

RESULTS

The prevalence of incidental prostate FDG uptake was approximately 1.8%. Among 198 incidental lesions, 100 patients had further examinations; 20 lesions were confirmed to be malignant, while 80 lesions were benign. After logistic regression analysis, age, site, and the maximum standard uptake value were the potent predictors for differentiation of malignant prostate lesions.

CONCLUSION

When focal FDG uptake in the peripheral zone of prostate is detected, especially in elderly men, further clinical evaluation is recommended.