FCCC LOGO Faculty Publications
Xiong W , Li J , Ma CM
Effect of patient variation on standard- and hypo-fractionated radiotherapy of prostate cancer
Physics in Medicine and Biology. 2005 ;50(7) :1483-1492
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Abstract
Recent publications suggested that the ?/? ratio in the well-known linear quadratic (LQ) model could be as low as 1.5 Gy for prostate cancer, indicating that prostate cancer control might be very sensitive to changes in the dose fractionation scheme. This also suggests that the standard-fractionation scheme based on large ?/? ratios may not be optimal for the radio-therapeutic management of prostate cancer. Hypo-fractionated radiotherapy for prostate cancer has received more attention recently as an alternative treatment strategy, which may lead to reduced treatment time and cost. However, hypofractionated radiotherapy may be more sensitive to patient variation in terms of disease control than standard-fractionated radiotherapy. The variation of LQ parameters a and ? for a patient population may compromise the outcome of the treatment. This effect can be studied by the introduction of the ?? and ?? parameters, which are the standard deviations of Gaussian distributions around ?0 and ?0. The purpose of this study is to examine the effect of patient variation in a and ? on tumour control probability for standard- and hypo-fractionated radiotherapy of prostate cancer. The tumour control probability based on the LQ model is calculated using parameters ?, ?, ?? and ??. Our results show that ?? is an important parameter for radiotherapy fractionation, independent of the ?/? ratio. A large ??will result in a significant increase in the radiation dose required to achieve the same 95% TCP. Compared with the standard-fractionated scheme, ?? has a smaller effect on hypo-fractionated treatment at lower ?/? ratios. On the other hand, for lower ?/? ratios, the ? term also plays a more important role in cell-killing and therefore the patient variation parameter ?? must be considered when designing a new dose fractionation scheme. © 2005 IOP Publishing Ltd.
Notes
00319155 (ISSN) Cited By: 0; Export Date: 25 May 2006; Source: Scopus CODEN: PHMBA; DOI: 10.1088/0031-9155/50/7/011 Language of Original Document: English Correspondence Address: Xiong, W.; Department of Radiation Oncology; Fox Chase Cancer Center Philadelphia, PA 19111, United States; email: w_xiong@fccc.edu References: Brenner, D.J., Hall, E.J., Fraction and protraction for radiotherapy of prostate carcinoma (1999) Int. J. Radiat. Oncol. Biol. Phys., 43, pp. 1098-1101; Brenner, D.J., Hall, E.J., Low ?/? values for prostate cancer appear to be independent of modeling details (2000) Int. J. Radiat. Oncol. Biol. Phys., 47, pp. 538-539; Duschesne, G.M., Peters, L.J., What is the ?/? ratio for prostate cancer? Rational for hypofractionated high-dose-rate brachytherapy (1999) Int. J. Radiat. Oncol. Biol. Phys., 44, pp. 747-748, editorial; Fowler, J., Chappell, R., Ritter, M., Is ?/? for prostate tumors really low? (2001) Int. J. Radiat. Oncol. Biol. Phys., 50, pp. 1021-1031; King, C.R., Fowler, J.F., A simple analytic derivation suggests that prostate cancer ?/? ratio is low (2001) Int. J. Radiat. Oncol. Biol. Phys., 51, pp. 213-214; King, C.R., Mayo, C.S., Is the prostate ?/? ratio of 1.5 from Brenner and Hall a modeling artifact? (2000) Int. J. Radiat. Oncol. Biol. Phys., 47, pp. 536-538; Moiseenko, V., Effect of heterogeneity in radiosensitivity on LQ based isoeffect formalism for low ?/? cancers (2004) Int. J. Radiat. Oncol. Biol. Phys., 43, pp. 499-502; Nahum, A.E., Incorporating clinical measurements of hypoxia into tumor local control modeling of prostate cancer: Implications for ?/? ratio (2003) Int. J. Radiat. Oncol. Biol. Phys., 57, pp. 391-401; Nahum, A.E., Chapman, J., In response to Dr Want et al (2005) Int. J. Radiat. Oncol. Biol. Phys., 61, pp. 310-311; Nahum, A.E., Sanchez-Nieto, B., Tumor control probability modeling: Basic principles and applications in treatment planning (2001) Physica Medico, 17, pp. 13-13; Wang, J., Mayr, N., Li, A., Stewart, R., Modeling prostate cancer: In regards to Nahum et al (2005) Int. J. Radiat. Oncol. Biol. Phys., 61, pp. 309-61310; Webb, S., Nahum, A.E., A model for calculating tumor control probability in radiotherapy including the effects of inhomogeneous distributions of dose and clonogenic cell density (1993) Phys. Med. Biol., 38, pp. 653-666.