Bladder tumours are classified by tumour stage and subtype and by grade of aggressiveness of the tumour cells. Staging is a standard way to describe the extent of cancer spread. The kind of treatment you receive will depend on these elements.
Stage and subtype
Tumour stage is based on whether or not the cancer has invaded the bladder wall (Fig.1). This information is important for determining additional treatment and risk profile (the risk of recurrence of the disease).
Stages Ta, T1, and CIS indicate non–muscle invasive bladder cancer (Fig. 1):
- Ta tumours are confined to the bladder lining (shown as ‘mucosa’).
- T1 tumours have invaded the connective tissue under the bladder lining but have not grown into the muscle of the bladder wall.
- CIS tumours are flat velvet-like tumours that are confined to the bladder lining (shown as ‘mucosa’).
Stages T2, T3, and T4 indicate muscle-invasive bladder cancer, with tumours that have grown beyond the mucosa into the bladder wall (Fig. 1). Additional imaging of the abdomen and thorax is used to detect tumour spread outside the bladder for staging of this type of bladder cancer.
Imaging for staging invasive bladder cancer
CT and magnetic resonance imaging (MRI scan) are the techniques used for staging invasive bladder cancer. A combination of positron emission tomography (PET scan; uses a radioactive tracer) and CT is increasingly being used in many centres in Europe to enhance the ability of detecting the spread of bladder cancer to the lymph nodes or other organs.
Imaging is used for staging invasive bladder cancer to determine prognosis and to provide information for treatment selection. Tumour staging must be accurate to ensure the correct choice of treatment.
In staging of muscle-invasive bladder cancer, imaging determines:
- How far the tumour has grown into the bladder wall (extent of local tumour invasion)
- Whether cancer has spread to the lymph nodes
- Whether cancer has spread to the upper urinary tract or other distant organs
During examination of tissue under a microscope (histological analysis), the pathologist will grade the tumours according to their potential to grow (aggressiveness). High-grade tumours are more aggressive, and tissue is greatly altered in appearance. Low-grade tumours are less aggressive, and tissue is mildly altered in appearance.
Stratification into risk groups of non-muscle invasive bladder tumours
For non-muscle invasive bladder tumours, risk stratification is used to provide more precise treatment recommendations. Your doctor does this based on disease stage and grade and some other tumour-related factors, and study-based risk tables.
You will be assigned to one of three groups (low, intermediate, or high risk) based on your risk of recurrence and progression. This stratification is used to determine the treatment options that can be offered and the follow-up that will be needed.
- Low risk: Patients have a single small (<3 cm) tumour that is stage Ta (Fig. 1) and that is not likely to grow (low grade). Low-risk patients do not have CIS, which has a high risk of growing into the deeper layers of the bladder muscle tissue and spreading to other organs or lymph nodes.
- Intermediate risk: Patients with tumours that are not clearly either low or high risk are considered to have an intermediate risk of recurrence and progression.
- High risk: Patients are at high risk if their tumour is stage CIS or T1 or is aggressive (high grade). Multiple large (>3 cm) and recurrent tumours of stage Ta are also high risk.