What Long Term Affect Does Chemotherapy And/or Radiation Have On The Brain?

First, I did a chemo/radiation therapy, then a major surgery, another round of chemo and another surgery. The radiation I receiced was in the ‘bottom’ region and was the maximem/highest dose one can receive in that area for the remainder of my life. I became very depressed and lost some memory. Could any of these treatments alter a persons mind?? (not experience wise, but physically/medically wise)?