The medical records of 76 patients undergoing radiotherapy for locally advanced head and neck cancers at the University of Arizona, Department of Radiation Oncology, were retrospectively reviewed following institutional review board (IRB) approval. One patient consented for his clinical imaging to be published following de-identification. Patients were selected if they had naso-, oro-, and hypopharyngeal cancers and/or regional nodal metastases from head and neck primary tumors of any site.
All patients had PET-CT scans prior to treatment for staging purposes. Patients who had retropharyngeal lymph nodal metastases on the pre-treatment PET-CT were excluded. Head and neck MRI was not performed routinely except for patients with nasopharyngeal cancer because of its superiority in the detection of intracranial extension. All patients were treated with the whole field IMRT (Elekta) or IGRT (Helical Tomotherapy, Hi-Art II) with simultaneous integrated boost, from January 2006 to May 2011. Prior to treatment, each patient was simulated in the supine position with a head and neck aquaplast mask for treatment immobilization. A computed tomography (CT) scan with and without intravenous (IV) contrast for treatment planning was performed in the treatment position. The head and neck areas from the vertex to the mid thorax were scanned with a slice thickness of 3
mm CT scan with IV contrast to outline the tumor and grossly enlarged cervical lymph nodes for target volume delineation. Radiotherapy planning was performed on the CT scan without contrast to avoid possible interference of contrast density on radiotherapy isodose distributions. Diagnostic PET-CT scan planning for tumor imaging was also incorporated with CT planning for tumor imaging. A 0.5
cm bolus material was placed on any area of the skin involved by the tumor and on any palpable cervical lymph nodes. Normal organs at risk for complication were outlined for treatment planning (spinal cord, brain stem, bilateral cochlea, mandible, parotid glands, bilateral eyes, and oral cavity). For patients with definitive chemoradiation, the tumor and grossly enlarged lymph nodes (CTV1) on CT scan with a margin (PTV1) were treated to 70
Gy in 35 fractions (2
Gy/fraction). The margins were 5
mm to 1
cm all around CTV1 depending on anatomic location. The high risk-PTV2 (at least 1
cm around gross tumor and pathologic cervical lymph nodes) and low risk -PTV3 (subclinical regional lymph nodes with 5
mm margins) for tumor spread were treated respectively to 63
Gy and 56
Gy in 35 fractions, respectively. Patients undergoing postoperative radiation or chemoradiation were treated to 66
Gy, and 54
Gy in 33 fractions to PTV1, PTV2, and PTV3 respectively. Indications for postoperative chemoradiation were positive margins and/or lymph node metastases with extra-capsular extension. Minimal target coverage was 95% of the prescribed dose for all targets with at least 99% of the prescribed dose delivered to gross tumor and involved cervical lymph nodes. The lymph nodes in the ipsilateral neck including the retropharyngeal lymph nodes were treated to the base of skull if there was any cervical lymph node enlargement (or PET-positive lymph nodes). The retropharyngeal lymph nodes were outlined from the hyoid bone to the base of skull to include the Rouviere nodes based on the consensus guidelines [17
]. The retropharyngeal lymph nodes were treated to 5600
cGy (35 fractions) during exclusive chemoradiation, or 5400
cGy (33 fractions) during postoperative radiation or chemoradiation because of the risk for subclinical disease. Contralateral uninvolved lymph nodes were treated prophylactically with the C1 vertebrae as the superior border of the radiation field in order to spare the parotid gland. In case of bilateral regional metastases, both sides of the neck were irradiated to the base of skull to avoid any marginal miss. Mean dose to the parotid gland was constrained below 2600
cGy if there was no ipsilateral cervical lymph node enlargement. Dose constraints for other normal organs at risk (OAR) for complications were: Dmax to the spinal cord <45
Gy, Dmax to the brain stem <50
Gy, Dmax to the optic chiasm <45
Gy, and mandibular V70 <30% of the mandible.
Concurrent chemoradiation was recommended for all except for patients with thyroid malignancies (2). One patient with neuroendocrine tumor of the thyroid was treated with concurrent chemoradiation The type of chemotherapy regimen was left to the discretion of the medical oncologists depending on patient functional status and co-morbidities. Prophylactic percutaneous gastrostomy tubes feedings placement was recommended for all patients prior to radiotherapy because of the expected weight loss secondary to severe mucositis, dysphagia, and dysgueusia. Weekly complete blood count (CBC) and blood chemistry to assess renal function were performed during chemoradiation. Treatment breaks and weight loss were recorded during chemoradiation.
Acute and long-term toxicities were graded according to Radiotherapy Oncology Group (RTOG) group criteria (http://ctep.cancer.gov
All patients had a follow-up visit at one month, then regularly every three months following treatment. Clinical and direct endoscopic examination were performed at each follow-up visit to detect recurrent disease. A PET-CT scan was performed at four months and ten months, then yearly after treatment if there was no evidence of disease. PET-positive areas were biopsied to detect local recurrences and surgery and/or chemotherapy were carried out for salvage if the biopsy demonstrated malignancy. The PET-CT scans following radiotherapy were reviewed, compared to the pre-treatment PET-CT and discussed with the radiologist to assess for recurrent disease and specifically, the presence or absence of retropharyngeal lymph node metastases.