Preliminary analysis of the sequential simultaneous integrated boost technique for intensity-modulated radiotherapy for head and neck cancers

The aim of this study was to compare three strategies for intensity-modulated radiotherapy (imrt) for 20 head-and-neck cancer patients. for simultaneous integrated boost (sib),doses were 66 and 54 gy in 30 fractions for ptvboost and ptvelective,respectively. two-phase imrt delivered 50 gy in 25 fractions to ptvelective in the first plan,and 20 gy in 10 fractions to ptvboost in the second plan. sequential sib (seq-sib) delivered 55 gy and 50 gy in 25 fractions,respectively,to ptvboost and ptvelective using sib in the first plan and 11 gy in 5 fractions to ptvboost in the second plan. conformity indexes (cis) (mean ± sd) for ptvboost and ptvelective were 1.09 ± 0.05 and 1.34 ± 0.12 for sib,1.39 ± 0.14 and 1.80 ± 0.28 for two-phase imrt,and 1.14 ± 0.07 and 1.60 ± 0.18 for seq-sib,respectively. ci was significantly highest for two-phase imrt. maximum doses (dmax) to the spinal cord were 42.1 ± 1.5 gy for sib,43.9 ± 1.0 gy for two-phase imrt and 40.3 ± 1.8 gy for seq-sib. brainstem dmax were 50.1 ± 2.2 gy for sib,50.5 ± 4.6 gy for two-phase imrt and 47.4 ± 3.6 gy for seq-sib. spinal cord dmax for the three techniques was significantly different,and brainstem dmax was significantly lower for seq-sib. the compromised conformity of two-phase imrt can result in higher doses to organs at risk (oars). lower oar doses in seq-sib made seq-sib an alternative to sib,which applies unconventional doses per fraction. © 2016 the author 2016. published by oxford university press on behalf of the japan radiation research society and japanese society for radiation oncology.