According to new research, 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. This is despite the higher doses of radiation used in the IMRT group. The research conducted by Philadelphia-based Fox Chase Cancer Center was presented at the Annual Meeting of the American Society for Therapeutic Radiology and Oncology this week. 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. For the study, researchers analyzed data collected 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). Even though patients treated with IMRT had higher doses of radiation, there were fewer gastrointestinal side effects three years after treatment (6.3 percent for IMRT; 10.4 percent in 3D CRT). The research showed no statistically significant difference between the two treatment types for genitourinary side effects.