Bladder Cancer
Fast Facts:
- 4th most common cancer in men
- 1:26 men & 1:90 women
- Localized Disease: 5-year survival ≈ 69%
- Distant Disease: 5-year survival ≈ 6%
Types:
- Transitional cell carcinoma > 90%
- Squamous cell ≈ 5%
- Adenocarcinoma < 2%
Value of PET/CT Scan for Bladder Cancer:
Diagnosis: No current role for PET/CT. Cystoscopy and biopsy are required.
Initial Staging: If the lesion is invasive and cystectomy is contemplated, preoperative staging with PET/CT can be useful to assess regional nodal status and potential distant metastatic disease.
Recurrence & Restaging:
- PET/CT is utilized for patients with known or suspected recurrent disease (or at high risk for recurrence).
- Distinguishing recurrence from post-therapeutic inflammation.
Assessing Response to Therapy & Prognosis:
Assess success or failure of therapy, and ultimate outcome/prognosis.
What We Report:
The size, metabolic activity & location of the primary lesion and representative metastatic lesions are reported.
Primary Lesion: PET/CT of limited value for primary lesion.
- As FDG is excreted in urine, the bladder is intensely avid on PET/CT studies, markedly limiting (often precluding) metabolic assessment of a bladder lesion.
- To attempt metabolic assessment of a bladder mass, it is essential to first manually decrease the image intensity of the scan. If the mass has greater avidity than urine on these manually “turned-down” images, then it can be called FDG-avid.
- C11-Choline, C11-Acetate and C11-Methionine, may prove useful, as they demonstrate only minimal urinary excretion.
Metastatic Disease:
- Direct invasion of adjacent structures and peritoneal cavity.
- Lymphatic spread to regional and distant lymph nodes.
- Hematogenous spread, often to bones, lungs, and liver.
False Negatives:
- Masking of metabolic activity by FDG-avid urine.
- Primary lesions < 8.0 mm (“beneath the resolution of PET”)
- Nodes or metastatic deposits < 8.0 mm (“beneath the resolution of PET”)
False Positives:
- Post-therapeutic inflammatory changes in post-operative patients.
Case 1
Case 1 (Image 2)
To better evaluate potential FDG-avid bladder lesions, we manually decrease the activity of the bladder (as we do when evaluating the brain), attempting to differentiate potential FDG-avid lesions from normal hypermetabolic urine.
Case 1 (Image 3)
Axial images demonstrate the “misregistration” that occurs with the bladder on a PET/CT scan. Because of the time delay between the CT portion of the exam and the completion of the PET exam, the bladder will be more distended on the PET images than on the CT images, leading to “malalignment” when the images are fused, another limitation of bladder assessment with PET/CT. Arrows denote the “earlier” bladder margin from the CT scan superimposed on the PET image.
Case 1 (Images 4)
Coronal images also demonstrate the “misregistration” that occurs because of the time delay between the CT portion of the exam and the completion of the PET exam (arrows denote the “earlier” bladder margin from the CT scan superimposed on the PET image).
Case 2
Case 2 (Image 2)
Manually decreasing the activity of the bladder will permit at least a limited evaluation of potential FDG-avid lesions. In this case, the manipulated image suggests possible ill-defined increased metabolic activity involving the right bladder wall.
Case 2 (Image 3)
CT image clearly shows a bladder mass. The normal fused image, however, is non-diagnostic, as the normal hyperintense metabolic activity of urine in the bladder precludes evaluation of the mass’ potential FDG uptake.
Case 2 (Image 4)
Manually decreasing the intensity of the bladder reveals the mass to be FDG-avid (arrows). Although still difficult to assess, the activity of the mass appears slightly more intense than the adjacent urine.
Case 3
Case 3 (Image 2)
CT image clearly shows the patient’s known bladder cancer. The normal fused image, however, is non-diagnostic, as the normal hyperintense metabolic activity of urine in the bladder precludes evaluation of the mass’ FDG uptake.
Case 3 (Image 3)
Manually decreasing the activity of the bladder will often permit at least a limited evaluation of potential FDG-avid lesions. In this case, the manipulated image is not very helpful, as the measured metabolic activity of this mass is relatively iso-intense to normal hypermetabolic urine (does the SUV reflect the activity of the mass or just normal urine activity?).
Case 3 (Image 4)
Multiple FDG-avid pulmonary metastases.
Case 3 (Image 5)
Intense focus of uptake corresponding only to fat in the inter-atrial septum, consistent with lipomatous hypertrophy of the inter-atrial septum. This is typically of no clinical significance.
Case 4
Case 4 (Image 2)
CT image clearly shows the patient’s known bladder cancer. The normal fused image is non-diagnostic, as the normal hyperintense metabolic activity of urine in the bladder precludes evaluation of the mass’ FDG uptake.
Case 4 (Image 3)
Manually decreasing the activity of the bladder will often permit a limited evaluation of potential FDG-avid bladder lesions. In this case, the manipulated image demonstrates the mass to be of greater intensity than the surrounding hypermetabolic urine, consistent with active malignancy.
Case 4 (Image 4)
Two FDG-avid metastatic right pelvic lymph nodes.
Case 4 (Image 5)
Clustering of small FDG-avid metastatic right common iliac chain lymph nodes.
Case 4 (Image 6)
Intense FDG uptake involving the masseter muscles, without associated soft tissue mass. This represents benign muscle activation (the patient confessed to sneaking Nicorette gum after FDG injection).
Case 5
Case 5 (Image 2)
Metastatic FDG-avid bilateral inguinal lymph nodes.
Case 5 (Image 3)
FDG-avid metastatic left common iliac chain lymph node.
Case 5 (Image 4)
FDG-avid metastatic left pelvic lymph node.
Case 5 (Image 5)
MIP and fused images demonstrate the renal excretion of FDG to appear more “prominent” than normal. This reflects mild fullness of the renal collecting systems commonly seen in patients with cystectomy and urinary diversion.
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