Stage 4 Bladder Cancer Classification
Stage 4 bladder cancer is written as either Stage IVA or Stage IVB, depending on the extent of metastatic spread, using the AJCC TNM staging system (8th edition). 1, 2
Stage IVA Classification
Stage IVA bladder cancer includes two distinct presentations 1:
- T4b, any N, M0: Extravesical tumor invading the pelvic wall and/or abdominal wall, without distant metastases 1
- Any T, any N, M1a: Any primary tumor with distant metastasis limited to lymph nodes beyond the common iliac nodes 1
These patients are considered to have a "good prognostic risk category within stage IV disease," which expands their treatment options compared to Stage IVB 1.
Stage IVB Classification
Stage IVB is defined as any T, any N, M1b disease—meaning non-lymph node distant metastases to organs such as lung, liver, or bone. 1 This represents the most advanced stage with the poorest prognosis 1.
TNM Component Breakdown
The staging notation uses three components 2, 3:
- T stage: Depth of tumor invasion into bladder wall and adjacent structures 2
- N stage: Number and location of metastatic regional lymph nodes 2
- M stage: Presence and location of distant metastases 2
Clinical Documentation Format
When documenting Stage 4 bladder cancer, specify 2, 3:
- Clinical staging (cTNM): Based on physical examination, imaging, and cystoscopy 3
- Pathological staging (pTNM): Based on surgical specimens when available 3
- Example notation: "cT4b N2 M0" for Stage IVA or "cT3 N1 M1b" for Stage IVB 3
Critical Staging Pitfall
Clinical staging frequently understages patients compared to final pathology—up to 45% of bladders are clinically understaged after TURBT. 2, 4 This occurs primarily because imaging cannot accurately predict true depth of invasion, and size-based criteria miss microscopic metastases in normal-sized lymph nodes 1, 2.