Patterns of metastasis in muscle-invasive bladder cancer (pT2-4): An autopsy study on 367 patients

Metastatic status is an essential determinant of prognosis of patients with muscle-invasive bladder cancer treated by cystectomy, and preoperative metastases detection is crucial for treatment selection in these patients. To better understand the metastatic behavior of bladder tumors, autopsies of patients with muscle-invasive bladder carcinomas (pT2-4) were evaluated.

Protocols and histologic sections from autopsies of 367 patients with pT2-4 bladder cancer were reviewed.

Metastases were found in 251 of 367 patients (68%). The most frequent sites of metastases were regional lymph nodes (90%), liver (47%), lung (45%), bone (32%), peritoneum (19%), pleura (16%), kidney (14%), adrenal gland (14%), and the intestine (13%). There was no difference in the frequency and location of metastases between 308 transitional cell carcinomas and 38 squamous cell carcinomas. The frequency of metastases increased with local tumor extension (patients with cystectomy: pT2, 36%; pT3a, 45%; pT3b, 69%; pT4, 79%; p < 0.0001). For all pT classifications, the frequency of metastases was slightly higher in patients treated by cystectomy (metastases in 45% of 29 pT2 and 89% of 28 pT4 tumors) than in patients without cystectomy (36% of pT2 and 79% of pT4 tumors).

These results argue against relevant clinical differences between histologic tumor types. The high frequency of metastases in patients having undergone cystectomy indicates that metastasis often occurs before the time of diagnosis. This emphasizes the need for a better prediction of the metastatic capability of these tumors at the time of diagnosis.