Dose plans for 60 left-sided breast cancer patients were analysed. All patients were planned with tangential fields for whole breast irradiation. Dose distributions were corrected to the equivalent dose in 2?Gy fractions (EQD2) using the linear quadratic model for five different fractionation schedules (50?Gy/25 fractions and four hypofractionation regimens) and for a range of ¦Á/¦Â values (0-5?Gy). The mean EQD2 to the heart () and the volume receiving 40?Gy (), both as calculated from the EQD2 dose distributions, were compared between schedules.
For ¦Á/¦Â?=?3?Gy, favours hypofractionation for 40?Gy/15 fractions, 39?Gy/13 fractions and 42.5?Gy/16 fractions, but not for 41.6?Gy/13 fractions. All of the hypofractionation schedules result in lower compared with normofractionation. These results hold as long as ¦Á/¦Â???1.5?Gy. If the heart is blocked from the treatment beam, the fraction size-corrected dose is lower for the first three hypofractionation schedules, compared with normofractionation, even for ¦Á/¦Â?=?¡«1?Gy.
For standard tangential field whole breast irradiation, most of the examined hypofractionation schedules are estimated to spare the heart when compared with normofractionation. The dose to the heart, adjusted for fraction size using the linear quadratic model, will generally be lower after hypofractionated compared with normofractionated schedules, even for very low values of ¦Á/¦Â.
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