GI toxicity, radiation therapy, and androgen deprivation

For men undergoing the combination of external beam radiation therapy (EBRT) and androgen deprivation therapy (ADT), for treatment of prostate cancer there is a significant risk for gastrointestinal (GI) toxicity over time.

A new study from researchers at Fox Chase Cancer Center has now shown that this risk for GI toxicity is significantly lower among men who are treated with intensity-modulated radiation therapy (IMRT) as opposed to traditional three-dimensional conformal beam radiation therapy (3D-CRT).

Sharma et al. carried out a retrospective analysis of patients receiving either 3D-CRT + ADT (n = 170) or IMRT + ADT (n = 123) between 1992 and 2004. The mean radiation dose delivered was 76 Gy for both categories of radiation.

Key results of the study are as follows:

  • Average (mean) follow-up was 86 ± 29.3 months for the 3D-CRT group and 40 ± 9.7 months for the IMRT group.
  • Acute GI toxicity was significantly more common among the 3D-CRT group compared to the IMRT group (odds ratio [OR] = 4)
  • The risk for acute GI toxicity was independent of the duration of ADT (i.e., < 6 vs. ≥ 6 months).
  • The time to development of late GI toxicity was significantly longer in the IMRT group.
  • The 5-year Kaplan-Meier estimate for GI toxicity of grade 2 or higher was 20 percent for 3D-CRT and 8 percent for IMRT (p = 0.01).
  • On multivariate analysis, late GI toxicity if grade 2 or higher was more prevalent in the 3D-CRT patients (hazard ratio [HR] = 2.1) .

Additional information about this study is available in a media release from the American Society for Radiation Oncology (ASTRO)

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