PURPOSE: Recent publications indicate alpha/beta for prostate carcinoma could be lower than assumed. Therefore, hypofractionation might increase the therapeutic ratio. However, patient repositioning and organ motion may affect hypofractionated treatments more than conventional treatments. Our purpose is to evaluate the potential impact of geometric uncertainties on hypofractionated treatments. METHODS AND MATERIALS: Tumor control probability (TCP) and normal tissue complication probability (NTCP) are calculated for simulated conventional and hypofractionated treatments, assuming alpha/beta of 1.5 Gy for prostate and 3.0 Gy for rectum. A Monte Carlo simulation randomly samples systematic and random displacements and produces the cumulative dose distribution for the prostate and rectum. The limiting number of fractions and the impact of different alpha/beta values are also explored. RESULTS: A consistent but small reduction in TCP is seen with hypofractionation (generally <1%) as a result of geometric uncertainties. Escalated hypofractionation seems to allow large TCP gains ( approximately 20%) without increasing NTCP. Treatments of five fractions seem to affect outcome minimally. The alpha/beta value has a much greater impact on TCP than geometric uncertainties. CONCLUSION: The potential increased influence of geometric uncertainties on hypofractionation seems small. Limited knowledge of radiobiologic response is likely a greater obstacle to prostate hypofractionation than geometric uncertainties.
PURPOSE: Recent publications indicate alpha/beta for prostate carcinoma could be lower than assumed. Therefore, hypofractionation might increase the therapeutic ratio. However, patient repositioning and organ motion may affect hypofractionated treatments more than conventional treatments. Our purpose is to evaluate the potential impact of geometric uncertainties on hypofractionated treatments. METHODS AND MATERIALS: Tumor control probability (TCP) and normal tissue complication probability (NTCP) are calculated for simulated conventional and hypofractionated treatments, assuming alpha/beta of 1.5 Gy for prostate and 3.0 Gy for rectum. A Monte Carlo simulation randomly samples systematic and random displacements and produces the cumulative dose distribution for the prostate and rectum. The limiting number of fractions and the impact of different alpha/beta values are also explored. RESULTS: A consistent but small reduction in TCP is seen with hypofractionation (generally <1%) as a result of geometric uncertainties. Escalated hypofractionation seems to allow large TCP gains ( approximately 20%) without increasing NTCP. Treatments of five fractions seem to affect outcome minimally. The alpha/beta value has a much greater impact on TCP than geometric uncertainties. CONCLUSION: The potential increased influence of geometric uncertainties on hypofractionation seems small. Limited knowledge of radiobiologic response is likely a greater obstacle to prostate hypofractionation than geometric uncertainties.
Authors: Mary Feng; James M Balter; Daniel Normolle; Saroja Adusumilli; Yue Cao; Thomas L Chenevert; Edgar Ben-Josef Journal: Int J Radiat Oncol Biol Phys Date: 2009-04-22 Impact factor: 7.038
Authors: Siyuan Lei; Nathaniel Piel; Eric K Oermann; Viola Chen; Andrew W Ju; Kedar N Dahal; Heather N Hanscom; Joy S Kim; Xia Yu; Guowei Zhang; Brian T Collins; Reena Jha; Anatoly Dritschilo; Simeng Suy; Sean P Collins Journal: Front Oncol Date: 2011-12-08 Impact factor: 6.244