• Int. J. Radiat. Oncol. Biol. Phys. · Mar 2010

    Comparative Study

    Impact of fraction size on lung radiation toxicity: hypofractionation may be beneficial in dose escalation of radiotherapy for lung cancers.

    • Jin-Yue Jin, Feng-Ming Kong, Indrin J Chetty, Munther Ajlouni, Samuel Ryu, Randall Ten Haken, and Benjamin Movsas.
    • Department of Radiation Oncology, Henry Ford Hospital, Detroit, MI 48202, USA. jjin1@hfhs.org
    • Int. J. Radiat. Oncol. Biol. Phys. 2010 Mar 1; 76 (3): 782-8.

    PurposeTo assess how fraction size impacts lung radiation toxicity and therapeutic ratio in treatment of lung cancers.Methods And MaterialsThe relative damaged volume (RDV) of lung was used as the endpoint in the comparison of various fractionation schemes with the same normalized total dose (NTD) to the tumor. The RDV was computed from the biologically corrected lung dose-volume histogram (DVH), with an alpha/beta ratio of 3 and 10 for lung and tumor, respectively. Two different (linear and S-shaped) local dose-effect models that incorporated the concept of a threshold dose effect with a single parameter D(L50) (dose at 50% local dose effect) were used to convert the DVH into the RDV. The comparison was conducted using four representative DVHs at different NTD and D(L50) values.ResultsThe RDV decreased with increasing dose/fraction when the NTD was larger than a critical dose (D(CR)) and increased when the NTD was less than D(CR). The D(CR) was 32-50 Gy and 58-87 Gy for a small tumor (11 cm(3)) for the linear and S-shaped local dose-effect models, respectively, when D(L50) was 20-30 Gy. The D(CR) was 66-97 Gy and 66-99 Gy, respectively, for a large tumor (266 cm(3)). Hypofractionation was preferred for small tumors and higher NTDs, and conventional fractionation was better for large tumors and lower NTDs. Hypofractionation might be beneficial for intermediate-sized tumors when NTD = 80-90 Gy, especially if the D(L50) is small (20 Gy).ConclusionThis computational study demonstrated that hypofractionated stereotactic body radiotherapy is a better regimen than conventional fractionation in lung cancer patients with small tumors and high doses, because it generates lower RDV when the tumor NTD is kept unchanged.Copyright (c) 2010 Elsevier Inc. All rights reserved.

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