Volumetric tumor burden and its effect on brachial plexus dosimetry in head and neck intensity-modulated radiotherapy |
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Institution: | 2. Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia;3. Liverpool and Macarthur Cancer Therapy Centres, NSW, Australia;4. School of Physics, University of Sydney, NSW, Australia;5. South West Clinical School, School of Medicine, University of New South Wales, Australia;2. Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA;2. Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China;3. Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China;2. Department of Oncology, Western University, London, Ontario, Canada;3. Department of Medical Biophysics, Western University, London, Ontario, Canada |
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Abstract: | To determine the effect of gross tumor volume of the primary (GTV-P) and nodal (GTV-N) disease on planned radiation dose to the brachial plexus (BP) in head and neck intensity-modulated radiotherapy (IMRT). Overall, 75 patients underwent definitive IMRT to a median total dose of 69.96 Gy in 33 fractions. The right BP and left BP were prospectively contoured as separate organs at risk. The GTV was related to BP dose using the unpaired t-test. Receiver operating characteristics curves were constructed to determine optimized volumetric thresholds of GTV-P and GTV-N corresponding to a maximum BP dose cutoff of > 66 Gy. Multivariate analyses were performed to account for factors associated with a higher maximal BP dose. A higher maximum BP dose (> 66 vs ≤ 66 Gy) correlated with a greater mean GTV-P (79.5 vs 30.8 cc; p = 0.001) and ipsilateral GTV-N (60.6 vs 19.8 cc; p = 0.014). When dichotomized by the optimized nodal volume, patients with an ipsilateral GTV-N ≥ 4.9 vs < 4.9 cc had a significant difference in maximum BP dose (64.2 vs 59.4 Gy; p = 0.001). Multivariate analysis confirmed that an ipsilateral GTV-N ≥ 4.9 cc was an independent predictor for the BP to receive a maximal dose of > 66 Gy when adjusted individually for BP volume, GTV-P, the use of a low anterior neck field technique, total planned radiation dose, and tumor category. Although both the primary and the nodal tumor volumes affected the BP maximal dose, the ipsilateral nodal tumor volume (GTV-N ≥ 4.9 cc) was an independent predictor for high maximal BP dose constraints in head and neck IMRT. |
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Keywords: | Head and neck cancer Brachial plexus Gross tumor volume Dose-volume histogram |
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