Long-term side effects of radiation for endometrial cancer are generally due to radiation to the other organs inside the pelvis. These include the bowel, the bladder, and the vagina.
Radiation to the bowel can cause chronic diarrhea, bowel obstruction and fistula formation. A fistula is an abnormal connection or passageway between two organs that normally do not connect and requires surgical repair. Radiation to the bowel may also cause thinning of the blood vessels in the bowel which may cause bleeding even with the normal passage of the stool. This may require laser ablation to stop the bleeding.
Radiation to the bladder can cause stiffening of the bladder and therefore frequency of urination. Internal and/or external radiation to the vagina can cause narrowing of the vagina which would be progressive and would only be prevented by using a vaginal dilator. This is usually provided by the radiation oncologist after completion of radiation treatments.
Even though statistically the risk is relatively small, radiation would increase the risk of a secondary malignancy in the irradiated field. Therefore the above mentioned organs are potentially at risk of developing another cancer. Particularly in case of endometrial cancer one has to be aware of HNPCC or Hereditary nonpolyposis colorectal cancer. This is a syndrome with increased risk of colorectal and endometrial cancer but unfortunately two major factors in this syndrome are overlooked even by medical professionals. One is the fact that individuals affected by this syndrome do not have increased number of polyps in their colon or rectum. The second one is the fact that women with HNPCC are at higher risk for endometrial cancer that they are for colorectal cancer. Therefore often when a woman is diagnosed with endometrial cancer nobody is alarmed about their risk of colorectal cancer regardless of whether they get radiation therapy or not and they should be!