Radiation for prostate cancer may cause short- or long-term side effects. Even though radiation targets the cancer cells, normal body tissues near the tumor can be affected. Specifically, we are talking about the rectum, small intestine, bladder, urethra, bone marrow, and sexual organs. If these organs repair incompletely, the radiation effects may devolve into scar tissue. Most side effects from radiation resolve within 1-2 months after treatment. However, a minority of men encounter long-term problems.


There is one radiation-related side effect that has nothing to do with the surrounding organs—fatigue, which may begin to be noticeable after two weeks or so. The maximum level of fatigue usually occurs after about four weeks of treatment and persists until the end of the treatment. After the radiation is complete, normal energy levels typically recover in four to eight weeks. Moderate-intensity exercise—walking 30 minutes at least three days each week—substantially reduced fatigue.

Sexual Function

Patients may experience painful ejaculation due to inflammation during radiation. After radiation, patients may have a reduction of volume or dry orgasm. Up to 50% of patients have reported a decline in erectile function following radiation therapy. Medical treatment for ED after radiation is essentially the same as the treatment after surgery. A minority of men retain fertility after radiation. However, those desiring to preserve fertility should consider sperm banking prior to treatment. 

Genitourinary System (GU)

Due to the close anatomic relationship between the prostate, the bladder, and the urinary passage (called the urethra), portions of the GU system receive high doses of radiation. Symptoms such as increased nighttime urination, bladder spasms, and urinary urgency can appear approximately three to four weeks after the start of radiation. These symptoms occur in 30 to 40 percent of patients and typically resolve within one to two months. Rarely, patients report blood in the urine and painful urination during treatment. Such symptoms are often alleviated by Ibuprofen, Naprosyn, and Flomax. 

Late urinary complications requiring nonsurgical intervention have been reported in approximately 4 percent of the intensity-modulated radiation therapy (IMRT) patients and in about 16 percent of the seed implant patients. Complications requiring surgical intervention were noted in one percent of IMRT patients and two percent of the seed implant patients. Urinary incontinence during or after radiation therapy is extremely rare. Long-term scar formation leading to narrowing of the urethra (stricture) occurs in fewer than 2 percent of the patients. Patients with a prior history of transurethral resection of the prostate (TURP) have a higher risk of urinary stricture and urinary incontinence, especially after seed implantation. 


Short-term rectal side effects are usually mild in intensity and may include increased bowel movement frequency, painful defecation, and blood in the stool. These effects occur in 5 to 10 percent of patients and usually appear during the third or fourth week of treatment, reaching maximum intensity toward the end of treatment and dissipating four to eight weeks following completion of treatment. Most patients complete a standard course of radiation without any specific treatment, although in some cases dietary modifications and anti-inflammatory rectal steroid suppositories are required. 

Long-term rectal side effects are uncommon but may include chronic bowel frequency, rectal bleeding and pain. Steroid suppositories can ease symptoms, and in cases of significant rectal bleeding a formaldehyde enema has been shown to be effective. Severe long-term rectal complications, such as loss of anal sphincter control or “fistula” (a passageway connecting the rectum and another organ such as the bladder) occur in less than one in 1,000 treated patients. A new treatment called SpaceOAR may be helpful.  SpaceOAR is a gel injected between the prostate and the rectal wall to create a separation large enough that the rectal wall exposure to radiation is greatly reduced. 

Small Intestine

By virtue of its anatomic location in the peritoneal cavity above the prostate, the small intestine is usually unaffected. However, when pelvic lymph nodes and seminal vesicles are targeted, there is a risk of short- and long-term radiation effects on the small intestine. Short-term effects, called “enteritis,” can present as bloating, loss of appetite, nausea, colicky abdominal pain, or diarrhea. It can start after the second week of radiation and reach maximum intensity in the fourth week. Treatment is aimed at reducing the symptoms with anti-nausea and anti-diarrheal medications, as well as temporary diet modification to reduce fat and lactose content. These symptoms typically resolve within three months after the completion of treatment. Late small intestine side effects from radiation may develop after several months or years. Using modern techniques the incidence of long-term complications is expected to be less than 5 percent.

The Importance of Skillful Treatment

Many of the historical problems related to radiation have been solved with modern targeting techniques. Reduction in sexual potency is the most frequent problem, and intervention for recovery has a varied record of success. Urinary issues, with increased frequency or painful urination, are the second most common problem. GI problems are the least likely to occur. However, a small minority of men who undergo radiation therapy still encounter truly serious long-term GU and GI side effects that are difficult to manage. While treatment by knowledgeable experts can correct some treatment-related side effects, it’s certainly important to minimize the risk of side effects by carefully selecting skilled and experienced radiation therapists to perform the treatment.  




Henry Yampolsky, MD is a board certified Radiation Oncologist practicing at The Center for Radiation Therapy of Beverly Hills. He completed his Radiation Oncology specialty training at the University of Southern California/Norris Cancer Center and LAC+USC Medical Center. While at USC, Dr. Yampolsky acquired broad clinical expertise in the treatment of a wide range of cancers, as well as extensive experience with intensity modulated radiation therapy (IMRT), stereotactic radiotherapy, and gynecologic brachytherapy.