Staging of Urothelial Cancer: Cystoscopy and CT Evaluation Remain Standard

— MRI emerging as adjunctive tool

Illustration of a red arrow with the numbers 1-4 over two circles over a bladder with urothelial cancer
Key Points

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After confirmation of a diagnosis from tissue sampling, urothelial carcinoma is staged using multiple modalities to determine a treatment plan and estimate prognosis.

The evaluation typically includes a computed tomography (CT) scan of the abdomen and pelvis -- i.e., a CT urogram. This diagnostic procedure also serves as the first staging procedure. Staging also relies on cystoscopic assessment with transurethral resection of bladder tumor (TURBT) and imaging of the chest.

"Staging is very important. We have already partially staged the patient in whom a tumor is discovered in the bladder, ureter, or kidney with the CT urogram, which allows us to see if disease has metastasized, for example, to sites of disease within the liver and the lymph nodes -- not within the pelvis, but along the back, and to the adrenal gland," said Paras Shah, MD, of the Mayo Clinic in Rochester, Minnesota.

"We generally want to complete staging by also looking at the lung, because that is another [potential] site of metastasis," he added. "When a low-grade urothelial tumor is discovered on imaging, a chest x-ray is usually sufficient, because the likelihood of lung metastasis is low. But if it's a high-grade tumor and has roots [into the bladder wall], we want to get a CT scan of the chest because the sensitivity is much higher than x-ray to detect tumors in the lung."

If an abnormality is noted on the CT urogram -- for example, in a lymph node or in an organ -- additional work-up may be pursued. "In some patients in whom the CT scan is ambiguous, such as enlargement of a single lymph node [i.e., no diffuse preponderance of lymph node involvement], a positron emission tomography [PET] scan may be obtained to characterize the lymph node to see whether it's enlarged from the cancer or because it's reactive to inflammation around the cancer," Shah said. "The PET scan is done purely to evaluate for indeterminate findings on the CT urogram. It's not a standard of care for staging."

Emerging Role of MRI

Anthony Corcoran, MD, of New York University Langone Perlmutter Cancer Center in New York City, noted that although the gold standards for staging methods continue to be CT urography, TURBT, and chest imaging, interest in magnetic resonance imaging (MRI) of the pelvis to stage urothelial cancer is increasing -- specifically to gauge the depth of invasion of the tumor.

"Shaving out the tumor in the bladder is not a perfect science," Shah explained. "Sometimes it can be very difficult, and sometimes we don't get complete tumor resection. So prior to staging, with enough concern that the tumor has invaded the muscle, an MRI of the pelvis might be considered to determine the depth of tumor invasion within the bladder once a bladder tumor is suspected based on the cystoscopy and the CT urogram. But again, it's not the standard of care."

"There is some controversy over whether MRI can help predict the depth of invasion clinically before bladder removal more accurately than a CT scan or pathology," said Corcoran, who is also director of Urologic Oncology at NYU Langone Hospital - Long Island in Mineola, New York. The VI-RADS (Vesical Imaging Reporting and Data System) has been developed to specifically stage bladder cancer, similar to PI-RADs (Prostate Imaging Reporting and Data System) to estimate the likelihood of a significant prostate tumor using prostate MRI, and BI-RADS (Breast Imaging Reporting and Database System), a risk-assessment score to rate the results of breast imaging.

The main goal of VI-RADS was to overcome the risks and limitations of TURBT (i.e., bladder perforation and under- or over-staging) using noninvasive imaging. The system relies on a 5-point scale using multiparametric MRI to stratify the likelihood of invasion of the muscular layer of the bladder wall in a previously detected lesion.

A recently published meta-analysis of 20 studies "demonstrated excellent worldwide diagnostic performance of VI-RADS to determine pre-TURBT staging," the researchers wrote. "Our findings corroborate wide reliability of VI-RADS accuracy also between different centers with varying experience, underlying the importance that standardization and reproducibility of VI-RADS may confer to multiparametric magnetic resonance imaging for preoperative bladder cancer discrimination."

The ongoing BladderPath study is assessing whether cystoscopic staging can be substituted by multiparametric MRI, after bladder biopsy has confirmed the presence of bladder cancer, for determining if a patient will be submitted to conservative rather than radical interventions.

"The use of MRI is increasing, and I think that's good, because it can more accurately standardize staging before surgery, which can help us predict who needs chemotherapy before surgery and who doesn't, and who might be a good candidate for bladder-sparing protocols," Corcoran said.

TNM Staging System

The American Joint Committee on Cancer TNM (tumor, node, metastasis) system is the most commonly used method for staging bladder cancer. The system, which relies on the pathologic stage based on the results of physical examination, biopsy, imaging tests, and surgery, is considered to be more accurate than clinical staging, which relies only on the tests performed before surgery.

Combinations of the T, N, and M classifications are grouped to describe four stages of disease:

T (tumor) stages

  • T0: No evidence of primary tumor
  • Ta: Noninvasive papillary carcinoma
  • Tis: Carcinoma in situ: typically flat lesion
  • T1: The tumor has invaded the lamina propria, but without muscle involvement
  • T2: The tumor invades the muscularis propria, either superficially (stage T2a) or deeply (stage T2b)
  • T3: The tumor invades perivesical tissue, microscopically (pT3a) or macroscopically (pT3b)
  • T4: The tumor has spread to surrounding organs, such as the prostate, seminal vesicles, bowel, vagina, uterus, pelvic wall, or abdominal wall. In T4a, the tumor invades the prostatic stroma, uterus, or vagina; in T4b, the tumor invades the pelvic or abdominal wall

Lymph node (N) involvement

  • N0: No lymph node metastases
  • N1: Single regional lymph node metastasis in the true pelvis (perivesical, obturator, internal and external iliac, or sacral lymph node)
  • N2: Multiple regional lymph node metastasis in the true pelvis (perivesical, obturator, internal and external iliac, or sacral lymph node metastasis)
  • N3: Lymph node metastasis to the common iliac lymph nodes

Metastatic (M) stages

  • MX: Metastasis cannot be measured
  • M0: No spread to other parts of the body
  • M1: Distant metastasis

Read Part 1 of this series: Urothelial Cancer: Diagnostic Evaluation