Preventive sparing of spinal cord and brain stem in the initial irradiation of locally advanced head and neck cancers

Since reirradiation in recurrent head and neck patients is limited by previous treatment, a marked reduction of maximum doses to spinal cord and brain stem was investigated in the initial irradiation of stage III/IV head and neck cancers. Eighteen patients were planned by simultaneous integrated boost, prescribing 69.3 Gy to PTV1 and 56.1 Gy to PTV2. Nine 6 MV coplanar photon beams at equispaced gantry angles were chosen for each patient. Step‐and‐shoot IMRT was calculated by direct machine parameter optimization, with the maximum number of segments limited to 80. In the standard plan, optimization considered organs at risk (OAR), dose conformity, maximum dose [Formula: see text] to spinal cord and [Formula: see text] to brain stem. In the sparing plans, a marked reduction to spinal cord and brain stem were investigated, with/without changes in dose conformity. In the sparing plans, the maximum doses to spinal cord and brain stem were reduced from the initial values ([Formula: see text] and [Formula: see text]), without significant changes on the other OARs. A marked difference ([Formula: see text] and [Formula: see text]) was obtained at the expense of a small difference [Formula: see text] from initial [Formula: see text] coverage [Formula: see text]. Similar difference ([Formula: see text] and [Formula: see text]) was obtained compromising dose conformity, but unaffecting [Formula: see text] and with negligible decrease in [Formula: see text] ([Formula: see text] from the initial [Formula: see text]). A marked spinal cord and brain stem preventive sparing was feasible at the expense of a decrease in dose conformity or slightly compromising target coverage. A sparing should be recommended in highly recurrent tumors, to make potential reirradiation safer. PACS number: 87.55.D