title: Preventive sparing of spinal cord and brain stem in the initial irradiation of locally advanced head and neck cancers.
abstract: 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 &lt; 45 Gy to spinal cord and &lt; 50 Gy 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 (43.5 ± 2.2 Gy and 36.7 ± 14.0 Gy), without significant changes on the other OARs. A marked difference (-15.9 ± 1.9 Gy and -10.1 ± 5.7 Gy) was obtained at the expense of a small difference (-1.3% ± 0.9%) from initial PTV195% coverage (96.6% ± 0.9%). Similar difference (-15.7 ± 2.2 Gy and -10.2 ± 6.1 Gy) was obtained compromising dose conformity, but unaffecting PTV195% and with negligible decrease in PTV295% (-0.3% ± 0.3% from the initial 98.3% ± 0.8%). 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.
authors.affiliation: Regional Oncological Hospital, APSS. paolofarace@gmail.com.
authors.forename: Paolo
authors.initials: P
authors.lastname: Farace
authors.forename: Sara
authors.initials: S
authors.lastname: Piras
authors.forename: Sergio
authors.initials: S
authors.lastname: Porru
authors.forename: Federica
authors.initials: F
authors.lastname: Massazza
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Fadda
authors.forename: Ignazio
authors.initials: I
authors.lastname: Solla
authors.forename: Denise
authors.initials: D
authors.lastname: Piras
authors.forename: Maria Assunta
authors.initials: MA
authors.lastname: Deidda
authors.forename: Maurizio
authors.initials: M
authors.lastname: Amichetti
authors.forename: Marco
authors.initials: M
authors.lastname: Possanzini
mesh_terms: D001933:Brain Stem / Q000528:radiation effects*; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D009367:Neoplasm Staging; D059351:Organ Sparing Treatments; D011832:Radiation Injuries / Q000517:prevention & control*; D011835:Radiation Protection / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal; D050397:Radiotherapy, Intensity-Modulated; D013116:Spinal Cord / Q000528:radiation effects*