Reviewer: Charles E Stewart, MD PhD
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: November 18, 2005
Authors: G D e M eerleer , L V akaet , S M eersschout , et al.
Source: Int. J. Radiation Oncology Biol. Phys ., 60 (2004) 777-787 .
In the setting of external beam radiotherapy treatment of prostate cancer, Intensity Modulated Radiotherapy (IMRT) is rapidly becoming the norm and has replaced standard 3-dimesional conformal treatment in the majority of academic- and community-based centers. Inherent in substantial changes to radiation delivery techniques are not only potential changes in tumor control probabilities, but also potential changes in both acute and long-term side effects. The intent of this study was to examine acute toxicities of IMRT in patients with low, intermediate, and high risk for extra-prostatic disease. This study follows on the heels of a more comprehensive study by Zelefsky et al . (Int. J. Radiation Oncology Biol. Phys., Vol. 53, No. 5, pp. 1111–1116, 2002) that examined early toxicity in a larger patient cohort with extensive follow-up and more cleanly-parsed data.
The description of acute toxicity after IMRT for prostate cancer has been previously well characterized by Zelefsky et al . as described above, and remains the standard by which other articles should be compared. Their study involved 772 patients followed for over 4 years, and also measured initial biochemical failure rates. In addition, studies of IMRT for prostate cancer without daily localization of the prostate (such as the one summarized here) become uninterpretable. Numerous groups ( eg. Bentel et al , Int. J. Radiation Oncology Biol. Phys., Vol. 47, No. 1, pp. 247–253, 2000) have demonstrated considerable daily motion of the prostate independent of bony landmarks. Furthermore, the 7mm circumferential margin is tighter than most techniques using either 3-D conformal or IMRT techniques, particularly in the absence of daily prostate localization. Zelefsky's article reveals that toxicity only begins to manifest at three months, with pronounced amplification after that time.
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