Prostate cancer. Axial coloured magnetic resonance imaging (MRI) scan of the pelvis of a patient with prostate cancer. At centre is the prostate (pink), which has become enlarged due to cancer, the hip bones (cream) are at either side of the prostate. At upper centre is the bladder (yellow) which has become indented by the enlarged prostate, causing obstruction to the neck of the bladder and impairing urination, the main symptom of prostate cancer. The causes of prostate cancer are not known, but it is most prevalent in men over 50 years of age. Treatment is with hormone therapy, chemotherapy or surgery to remove the prostate.