Age-stratified distribution of metastatic sites in bladder cancer: A population-based analysis

Introduction: Urothelial carcinoma of the urinary bladder (UCUB) is the most common malignancy of the urinary tract. We examined the distribution of site-specific metastases in patients with UCUB according to age and we assessed contemporary recommendations proposed by guidelines with regard to distant metastases. Methods: Patients with metastatic UCUB (mUCUB) were abstracted from the Nationwide Inpatient Sample (1998-2007). Age was stratified into quartiles: ≤63, 64-72, 73-79 and ≥80 years. Cochran- Armitage trend test and multivariable logistic regression analysis tested the relationship between age and the rate of metastases. Finally, we identified patients at high risk of brain or bone metastases. Results: Within 7543 patients with mUCUB, 25%, 24%, 23%, 19%, 18% and 3% had lymph node, bone, urinary, lung and liver metastases, respectively. Overall, the rate of concomitant metastases was 29%. The rate of multiple metastatic sites decreased with increasing age (p <0.001). This was confirmed in patients with lung, bone, liver, urinary system and brain metastases (all p ≤ 0.04). The rate of bone metastases was 15.0% in patients with exclusive abdominal metastases and 40.0% in patients with abdominal, thoracic and brain metastases. The rate of brain metastases was 1% in patients with exclusive abdominal metastases and 7% in patients with thoracic and bone metastases. Our findings are limited by the retrospective nature of the analyses. Conclusions: We report a higher number of concomitant metastatic sites in young UCUB patients. Bone metastases are frequent in all patient groups, whereas brain metastases are common in UCUB patients with thoracic and/or bone metastases.