Presenter: J.M. Michalski Presenter's Affiliation: Dept. of Radiation Oncology, Washington University Medical School, St. Louis, MO, USA Type of Session: Scientific
Numerous previous studies have suggested that there is a dose-response relationship with radiation therapy (RT) used in the treatment of prostate cancer.
This study is a toxicity report on dose level IV (74 Gy) on RTOG 9406 for stage I&II adenocarcinoma of the prostate.
Materials and Methods
At a dose of 74 Gy, 256 pts are analyzable for toxicity.
2 Gy/day fractions were used and the dose was prescribed to the planning treatment volume (PTV).
Patients were stratified according to risk of seminal vesicle involvement (SVI).
For those pts with <15% risk of SVI (Group I), PTV included the prostate, while those with a 15% or greater risk (Group II) had an initial PTV that included the prostate and SV?s to 54 Gy followed by a conedown to the prostate-only.
Mean follow-up for Groups I &II, were 24 months and 20 months, respectively.
Acute toxicity at this dose level was remarkably low, with grade 3 effects seen in 1% of the Group I pts and 3% of the Group II pts.
Late grade 3 toxicity was much lower than expected when compared to historic controls on previous RTOG trials.
For Group I, 1 pt had a late grade 3 or higher toxicity, while 18 pts were predicted by the historical data. (p<.0001)
For Group II, 5 pts had toxicity, while 20 were predicted. (p=.001)
There was a trend for increased toxicity when fraction size was greater than 2 Gy.
Toxicity at the 74 Gy dose level was better than predicted by the historical data.
Longer follow-up is necessary to better assess late toxicity.
Information on toxicity is very important as radiation doses are escalated in the treatment of prostate cancer.
As the authors point out, longer follow-up is necessary to assess safety and efficacy of dose escalation.
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Oct 4, 2011 - Treatment of localized prostate cancer using intensity modulated radiation therapy is associated with a considerable reduction in late bowel and rectal side effects and significantly decreased rectal and bladder toxicity compared to three-dimensional conformal radiation therapy, according to a study presented the annual meeting of the American Society for Radiation Oncology, held from Oct. 2 to 6 in Miami Beach.