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Morgan PB, Hanlon AL, Horwitz EM, Buyyounouski MK, Uzzo RG, Pollack A
Radiation dose and late failures in prostate cancer
International Journal of Radiation Oncology Biology Physics (2007) 67:1074-1081.
Abstract
Purpose: To quantify the impact of radiation dose escalation on the timing of biochemical failure (BF) and distant metastasis (DM) for prostate cancer treated with radiotherapy (RT) alone. Methods: The data from 667 men with clinically localized intermediate- and high-risk prostate cancer treated with three-dimensional conformal RT alone were retrospectively analyzed. The interval hazard rates of DM and BF, using the American Society for Therapeutic Radiology and Oncology (ASTRO) and Phoenix (nadir + 2) definitions, were determined. The median follow-up was 77 months. Results: Multivariate analysis showed that increasing radiation dose was independently associated with decreased ASTRO BF (p < 0.0001), nadir + 2 BF (p = 0.001), and DM (p = 0.006). The preponderance (85%) of ASTRO BF occurred at :54 years after RT, and nadir + 2 BF was more evenly spread throughout Years 1-10, with 55% of BIT in <= 54 years. Radiation dose escalation caused a shift in the BF from earlier to later years. The interval hazard function for DM appeared to be biphasic (early and late peaks) overall and for the < 74-Gy group. In patients receiving >= 74 Gy, a reduction occurred in the risk of DM in the early and late waves, although the late wave appeared reduced to a greater degree. Conclusion: The ASTRO definition of BF systematically underestimated late BF because of backdating. Radiation dose escalation diminished and delayed BF; the delay suggested that local persistence may still be present in some patients. For DM, a greater radiation dose reduced the early and late waves, suggesting that persistence of local disease contributed to both. (c) 2007 Elsevier Inc.
Note
Publication Date: 2007-03-01.
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