Sex- and age-related differences in the distribution of bladder cancer metastases

Objective: Our objective was to investigate age- and sex-related differences in the distribution of metastases in patients with metastatic bladder cancer. Methods: Within the National Inpatient Sample database (2008-2015), we identified 7040 patients with metastatic bladder cancer. Trend test and Chi-square test analyses were used to evaluate the relationship between age and site of metastases, according to sex. Results: Of 7040 patients with metastatic bladder cancer, 5226 (74.2%) were men and 1814 (25.8%) were women. Thoracic, abdominal, bone and brain metastases were present in 19.5 vs. 23.0%, 43.6 vs. 46.9%, 23.9 vs. 18.7% and 2.4 vs. 2.9% of men vs. women, respectively. Bone was the most common metastatic site in men (23.9%) vs. lung in women (22.4%). Increasing age was associated with decreasing rates of abdominal (from 44.9 to 40.2%) and brain (from 3.2 to 1.4%) metastases in men vs. decreasing rates of bone (from 21.0 to 13.3%) and brain (from 5.1 to 2.0%) metastases in women (all P < 0.05). Finally, rates of metastases in multiple organs also decreased with age, in both men and women. Conclusions: The distribution of metastases in bladder cancer varies according to sex. Moreover, differences exist according to patient age and these differences are also sex-specific. In consequence, patient age and sex should be considered in the interpretation of imaging, especially when findings are indeterminate.