PURPOSE: There are reports of a high sensitivity of prostate cancer to radiotherapy dose fractionation, and this has prompted several trials of hypofractionation schedules. It remains unclear whether hypofractionation will provide a significant therapeutic benefit in the treatment of prostate cancer, and whether there are different fractionation sensitivities for different stages of disease. In order to address this, multiple primary datasets have been collected for analysis. METHODS AND MATERIALS: Seven datasets were assembled from institutions worldwide. A total of 5969 patients were treated using external beams with or without androgen deprivation (AD). Standard fractionation (1.8-2.0 Gy per fraction) was used for 40% of the patients, and hypofractionation (2.5-6.7 Gy per fraction) for the remainder. The overall treatment time ranged from 1 to 8 weeks. Low-risk patients comprised 23% of the total, intermediate-risk 44%, and high-risk 33%. Direct analysis of the primary data for tumor control at 5 years was undertaken, using the Phoenix criterion of biochemical relapse-free survival, in order to calculate values in the linear-quadratic equation of k (natural log of the effective target cell number), α (dose-response slope using very low doses per fraction), and the ratio α/β that characterizes dose-fractionation sensitivity. RESULTS: There was no significant difference between the α/β value for the three risk groups, and the value of α/β for the pooled data was 1.4 (95% CI = 0.9-2.2) Gy. Androgen deprivation improved the bNED outcome index by about 5% for all risk groups, but did not affect the α/β value. CONCLUSIONS: The overall α/β value was consistently low, unaffected by AD deprivation, and lower than the appropriate values for late normal-tissue morbidity. Hence the fractionation sensitivity differential (tumor/normal tissue) favors the use of hypofractionated radiotherapy schedules for all risk groups, which is also very beneficial logistically in limited-resource settings.
PURPOSE: There are reports of a high sensitivity of prostate cancer to radiotherapy dose fractionation, and this has prompted several trials of hypofractionation schedules. It remains unclear whether hypofractionation will provide a significant therapeutic benefit in the treatment of prostate cancer, and whether there are different fractionation sensitivities for different stages of disease. In order to address this, multiple primary datasets have been collected for analysis. METHODS AND MATERIALS: Seven datasets were assembled from institutions worldwide. A total of 5969 patients were treated using external beams with or without androgen deprivation (AD). Standard fractionation (1.8-2.0 Gy per fraction) was used for 40% of the patients, and hypofractionation (2.5-6.7 Gy per fraction) for the remainder. The overall treatment time ranged from 1 to 8 weeks. Low-risk patients comprised 23% of the total, intermediate-risk 44%, and high-risk 33%. Direct analysis of the primary data for tumor control at 5 years was undertaken, using the Phoenix criterion of biochemical relapse-free survival, in order to calculate values in the linear-quadratic equation of k (natural log of the effective target cell number), α (dose-response slope using very low doses per fraction), and the ratio α/β that characterizes dose-fractionation sensitivity. RESULTS: There was no significant difference between the α/β value for the three risk groups, and the value of α/β for the pooled data was 1.4 (95% CI = 0.9-2.2) Gy. Androgen deprivation improved the bNED outcome index by about 5% for all risk groups, but did not affect the α/β value. CONCLUSIONS: The overall α/β value was consistently low, unaffected by AD deprivation, and lower than the appropriate values for late normal-tissue morbidity. Hence the fractionation sensitivity differential (tumor/normal tissue) favors the use of hypofractionated radiotherapy schedules for all risk groups, which is also very beneficial logistically in limited-resource settings.
Authors: Amar U Kishan; Sang J Park; Christopher R King; Kristofer Roberts; Patrick A Kupelian; Michael L Steinberg; Mitchell Kamrava Journal: Br J Radiol Date: 2015-10-14 Impact factor: 3.039
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Authors: Philip S Boonstra; Jeremy M G Taylor; Beata Smolska-Ciszewska; Katarzyna Behrendt; Tomasz Dworzecki; Marzena Gawkowska-Suwinska; Brygida Bialas; Rafal Suwinski Journal: Br J Radiol Date: 2016-02-23 Impact factor: 3.039
Authors: Giuseppe Ferrera; Gianluca Mortellaro; Mariella Mannino; Giovanni Caminiti; Antonio Spera; Vanessa Figlia; Giuseppina Iacoviello; Gioacchino Di Paola; Rosario Mazzola; Antonio Lo Casto; Filippo Alongi; Maria Pia Pappalardo; Roberto Lagalla Journal: Radiol Med Date: 2015-05-24 Impact factor: 3.469
Authors: Michael Wahl; Martina Descovich; Erin Shugard; Dilini Pinnaduwage; Atchar Sudhyadhom; Albert Chang; Mack Roach; Alexander Gottschalk; Josephine Chen Journal: Technol Cancer Res Treat Date: 2016-07-08