What Are The Most Common Side Effects Of External Beam Radiation Treatment?

March 16, 2009 -- Question: What are the most common side effects of external beam radiation treatment?

Answer: So, for external radiation, or IMRT, the side effects can be divided into those that patients will experience during treatment, and side effects that may show up much later in time: months, or years later.

The short-term side effects that patients may experience during treatment, usually fall into the following categories. They may experience a little bit of fatigue. This doesn't impact on their daily activities, but they will feel a little more tired, and they may go to bed slightly earlier at night.

Men also may experience that they're going to urinate more frequently during the weeks of radiation, especially in the latter part of their radiation therapy: meaning in weeks four, five, six, seven, et cetera.

Sometimes men might experience a slight increase in having what I would call rectal side effects, or having more frequent bowel movements and this is because the prostate, as many men know from rectal exams, is right adjacent to the rectum. Part of the rectum does get inflamed, so they may see a small increase in bowel movements. They should not see diarrhea.

These side effects tend to go away over a month or two after they complete their course of radiation therapy. The long-term side effects of radiation therapy related to some of the normal tissues that are in the path of radiation field, no matter how conformal the radiation field. These side effects will impact again on the rectum and there's a small percentage, under 5 percent, that despite the greatest radiation techniques, may experience minor rectal bleeding a year or so later.

This is usually minor, and treated with very conservative means -- no surgery would ever be necessary. Another side effect would be the impact of radiation therapy on sexual potency, or does radiation therapy cause an increase in impotence.