IMRT versus 3D CRT for prostate cancer, new long-term data assesses side effects

New research findings show men have fewer long-term gastrointestinal side effects with intensity-modulated radiation therapy (IMRT) than with three-dimensional conformal radiation therapy (3D CRT) for prostate cancer treatment, despite the higher doses of radiation used in the IMRT group. These and other data, including long-term genitourinary side effects, were presented today at the 48th Annual Meeting of the American Society for Therapeutic Radiology and Oncology in Philadelphia.

Long-term data comparing 3D CRT for prostate cancer versus the use of IMRT is only now beginning to mature. Few other academic treatment centers have as much experience with 3D CRT and IMRT as Fox Chase.

Both techniques allow precise targeting of the cancer with multiple X-ray beams, but IMRT allows physicians to modulate the radiation dose intensity with far smaller radiation beams. Thus, doses of radiation to the bladder and rectum can be limited. Reducing radiation exposure to healthy normal tissue and other vital organs helps prevent once common side effects such as urinary frequency and diarrhea.

In the study presented today, researchers analyzed data collected prospectively from 1,417 patients treated at Fox Chase. Of these, 928 men were treated with 3D CRT (median follow-up of 63.3 months) and 489 men with IMRT (median follow-up of 29.9 months). The IMRT patients received higher doses of radiation.

Patients were matched for PSA level (prostate specific antigen, measured by a blood test and used to determine if prostate cancer is present), T-stage (palpable size) and Gleason score (tumor aggressiveness determined by pathologic testing). The researchers evaluated gastrointestinal side effects such as short-term diarrhea and longer-term bowel dysfunction and genitourinary side effects such as urinary frequency, urgency and, rarely, painful or difficult urination or obstructive symptoms.

"There were no differences in the reporting of acute gastrointestinal or genitourinary side effects for the two treatment modalities," explained Alexander Kirichenko, M.D., Ph.D., lead author of the study and a clinical fellow at Fox Chase at the time of the analysis. "However, as the data are beginning to mature, we're seeing more long-term gastrointestinal side effects in the men treated with 3D CRT." Kirichenko is now a radiation oncologist at Allegheny General Hospital in Pittsburgh, Pa.

Even though patients treated with IMRT had higher doses of radiation, there were fewer gastrointestinal side effects three years after treatment (6.3% for IMRT; 10.4% in 3D CRT). The research showed no statistically significant difference between the two treatment types for genitourinary side effects.

Kirichenko concluded, "Despite the specific findings pertaining to 3D CRT technique and the gastrointestinal side effects, men treated with either modality have acceptable rates of side effects at this point in our analysis particularly when compared to data from surgical outcomes."

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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