A Study of 68Gallium PSMA-PET/CT Scans in People With Bladder Cancer or Skin Cancer

This study is testing a special imaging scan using a radioactive tracer called 68Gallium PSMA (Ga-PSMA PET/CT) in people with bladder cancer or skin cancer (melanoma). Although this scan is already used in prostate cancer, researchers want to see if it can also help locate and track tumors in these other cancer types. **You may be eligible if...** - You have confirmed metastatic bladder cancer (urothelial carcinoma) with spread outside the pelvis, OR confirmed metastatic melanoma - You are 18 or older - Your functional status allows you to undergo a PET scan (able to lie still) - You have assessable/measurable lesions on imaging **You may NOT be eligible if...** - Your bladder cancer has only spread to pelvic lymph nodes or only to bones - You cannot lie flat or stay still for a PET scan - You are receiving active treatment for another cancer - You are pregnant - You are on a therapeutic trial where this scan would interfere Talk to your doctor to see if this trial is right for you.