Accelerated SIB-IMRT for Head and Neck Cancer

Patients were immobilized from head to shoulders with commercially available thermoplastic masks in the supine position. CT images (2 mm slice thickness) were acquired from the top of the vertex to the level of the carina with contrast agent infusion in non-operated patients.
We used an extended-field IMRT (EF-IMRT) technique, where the primary tumor was treated in one phase along with the regional lymph nodes. Irradiation was delivered with five or seven coplanar beam angles by a 6-MV dynamic MLC system (sliding window technique) (Varian Medical Systems, CA).
As previously described [1 (link)] an accelerated SIB- IMRT technique was performed with a daily dose of 2.00-2.35Gy (total dose: 63-75Gy) to the primary tumor and positive neck nodes in the definitive RT cases (n = 63) and a daily dose of 1.80-2.00Gy to a total dose of 60-66Gy in postoperative cases (n = 19). For intensity optimization the prescribed dose should encompass at least 95% of the PTV. Additionally, no more than 20% of any PTV would receive >110% of its prescribed dose, while no more than 1% of any PTV would receive <93% of the desired dose. The mean total treatment time was 45.3 days (32-55 days).
The protection of anatomical swallowing structures was routinely performed by drawing a laryngo-pharyngeal midline 'shielding' contour outside the PTVs in all cases. This sparing structure has been defined prospectively in January 2002, when we implemented IMRT clinically, and was provided to be used in all midline areas where no PTV was required. This structure may include esophageal, laryngeal, and pharyngeal structures. Aimed dose constraint for this midline shielding was a mean dose (Dmean) below 45Gy (Figure 1).
In oropharyngeal cancer patients, this structure was usually contoured from the level of the hyoid (below the lateral retropharyngeal lymph nodes, corresponding ~to the cervical vertebra 2/3, Figure 1) to the lowest level at which PTVs were drawn. In hypopharyngeal cancer patients, midline protection is often limited to some aspects of the larynx to just prevent laryngeal structures from full tumor dose.