Postoperative radiation therapy for squamous cell carcinoma of the head and neck

Fields for postoperative irradiation of a patient with advanced cancer of the laryngopharynx. (A) Typical simulation film. The initial “off-cord” reduction (50 Gy) is indicated by the dashed line and the final reduction (60 Gy) by the dotted line. Wires mark the surgical scars and stoma. Slanting line used on lower border reduces the length of spinal cord treated by the primary field, allows better caudal coverage of the mucosal surfaces while simultaneously bypassing the shoulders, and facilitates matching the low neck field. (B) Schematic diagram of low-neck field. The rectangle (solid line) represents the light field. The dashed lines denote the central axis. The shaded areas represent the blocked portions of the field (stacked lead blocks). The superior border of the neck field is the inferior border of the primary field. The actual line is treated only in the primary field. The upper border of the low-neck field assumes a V shape. In the midline of the patient, the apex of the V generally is at or close to the central axis, so that the portion of the low-neck portal that treats the spinal cord is nondivergent in its upper portion and diverges away from the primary fields in its lower portion. At the junction of the three fields, a short (2–3 cm) segment of spinal cord remains untreated by any of the three fields. (Reprinted with permission.⁸)

Averaged 6 MV dose distribution for larynx primary field with low-neck match and trachea block removed in an anthropomorphic head and neck phantom made of tissue-equivalent polyacrylamide gel with a 2-dimensional thermoluminescent dosimeter array in its sagittal midplane. The doses are normalized to the primary field's central axis dose. (Reprinted with permission.³⁸)

Typical portal after a hemimandibulectomy, partial maxillectomy, and radical neck dissection for a pathologic T4N0 retromolar trigone lesion. (A) Field reductions were made at 45 Gy (dashed line) and 60 Gy (dotted line). (B) The low neck received 50 Gy given dose (at Dmax) in 25 fractions. The larynx and a segment of the spinal cord were shielded by a tapered midline block. (Reprinted with permission.⁸)

Averaged ⁶⁰Co dose distribution for oropharynx field with low-neck match and larynx block. The dose distribution was obtained using an anthropomorphic head and neck phantom and a 2-dimensional thermoluminescent dosimeter array. The doses are shown as a percentage of the central axis dose. (Reprinted with permission.³⁸)

Local-regional control according to surgical margin. Other includes margins that were close, contained dysplasia, or carcinoma in situ or were initially positive but negative after re-resection. (Reprinted with permission.²⁰)

Local-regional control according to the number of indications for postoperative radiotherapy. (Reprinted with permission.²⁰)