Rectal cancer occurs when cancer cells start developing in the rectum. Symptoms of rectal cancer are blood in stool, constipation, and diarrhoea. After the best rectal cancer doctor diagnoses the cancer and determines its stage, treatment is prescribed. Here, we will look at the different stages of rectal cancer. Different stages of rectal cancer The different stages of rectal cancer. After the best rectal cancer doctor diagnoses the cancer and determines its stage, treatment is prescribed.