70 year old female complains that "Blood in feces"

70 year old female complains that “Blood in feces”. Weight loss is obvious. Abdomen examination revealed abdominal pain and masses. stool occult blood positive, CBC: Hb: 7mg/dl
The likely causes of GI bleeding at this age is?
Daignosis to confirm?

Old age + anemic + occasional blood in stool + occult blood test positive : always rule out first Colon Ca : go for Colonoscopy