Fluorodeoxyglucose-positron-emission tomography imaging of head and neck squamous cell cancer

Abstract

The hybrid technique of PET/CT has significantly impacted the imaging and management of HNSCC since its introduction in 2001 and has become the technique of choice for imaging of this cancer. Diagnostic FDG-PET/CT is useful for identification of an unknown primary tumor, delineation of extent of primary tumor, detection of regional lymph node involvement even in a normal-sized node, detection of distant metastases and occasional synchronous primary tumor, assessment of therapy response, and long-term surveillance for recurrence and metastases. The role of PET/CT is evolving in radiation therapy planning. Combined diagnostic PET/CT provides the best anatomic and metabolic in vivo information for the comprehensive management of HNSCC.

Fig 1.

Surgical planning and metabolic staging. A 50-year-old man with T4N2bM0 SCC of the right tonsil and base of the tongue. The contrast-enhanced CT component of the PET/DCT provides the high-resolution imaging necessary for surgical planning (red arrows), with the tumor involving the right tonsil and tongue base. The PET component of the PET/DCT provides the metabolic information about the primary tumor and locoregional and distant metastatic disease. The patient underwent resection with pectoralis flap reconstruction and concurrent chemoradiation. A and B, Contrast-enhanced CT of PET/CT. C−E, Fused PET/CT images. FDG uptake provides the primary tumor and metastatic lymph node metabolism (yellow arrows).

Fig 2.

Detection of unknown primary tumor. A 58-year-old man who presented with a right neck mass. A neck CT shows multiple enlarged necrotic right level II, III, and IV lymph nodes. FNA of the right level III node showed a metastatic poorly differentiated carcinoma with extensive necrosis. PET/CT showed a 1.0 × 1.2 cm hypermetabolic (gold arrow) and enhancing (red arrow) lesion at the right base of the tongue, large nodes in the right levels II/III, an 8-mm node at level IV, and no left-sided nodes or distant metastases. Direct laryngoscopy with biopsy and cervical esophagoscopy showed no lesions, but palpation showed a 1-cm firm right base of tongue lesion not crossing the midline, which was pathologically proved to be SCC. PET/CT is useful in identifying the unknown primary tumor in approximately one-third of patients after physical examination, anatomic cross-sectional imaging, and endoscopy. A−C, Fused PET/CT images. D−F, Contrast-enhanced CT of the PET/CT.

Fig 3.

Failure to detect an unknown primary tumor. A 50-year-old man who underwent a dental extraction in which the oral surgeon incidentally identified a right-sided neck mass that was tender to touch. FNA revealed moderate to poorly differentiated SCC. PET/DCT demonstrates FDG hypermetabolic (gold arrow) and enhancing (red arrow) lymphadenopathy in the right levels I-III and fails to reveal a primary lesion. Same-day rigid esophagoscopy, direct laryngoscopy, nasal endoscopy with biopsy of the base of the tongue bilaterally, and tonsillectomy showed no tumor. The patient was treated in all potential mucosal primary sites and the bilateral neck with IMRT to a dose of 69.96 Gy in 33 fractions with concurrent cisplatin. A, C, and D, Fused PET/CT images. B, Contrast-enhanced CT of the PET/CT.

Fig 4.

Perineural spread. A 65-year-old woman diagnosed with T4N0M0 SCC of the skin of the left upper lip and perineural spread along infraorbital nerve and VI to the skull base. PET/DCT demonstrates a hypermetabolic and enhancing mass in the left upper lip extending along the infraorbital nerve and at the skull base (gold arrows). MR imaging demonstrates these findings (red arrows) with higher resolution. The perineural spread is better depicted on the MR imaging than PET/CT due to higher resolution and small-volume disease along the nerve. A, B, and D, PET/DCT fused images. C, Contrast-enhanced coronal CT scan. E and G, Coronal T1 pregadolinium images. F and H, Postgadolinium coronal T1 images.

Fig 5.

Staging. A 62-year-old man with a stage IVa (T2 N2cM0) SCC of the tongue with a central necrotic right IB (red arrow) and right IIA (yellow arrow) FDG hypermetabolic lymphadenopathy. The left IIA lymph node (<10 mm) demonstrates FDG hypermetabolism, proved pathologically to be metastatic. Even smaller lymph nodes with apparent mild FDG uptake due to partial volume may harbor metastatic deposits.

Fig 6.

Radiation therapy planning. A, Planning CT GTV in red and PTV in blue. Green and aqua contours represent elective nodal volumes. B, PET. C, Rigid fusion of planning CT and PET for radiation planning. The PET/CT scan was obtained in the treatment position with rigid immobilization in a thermoplastic head and neck mask.

Fig 7.

Therapy assessment, complete response. A 39-year-old male patient with a stage IVa (T4N3M0) SCC of the right tonsil who underwent induction chemotherapy. A postinduction therapy PET/DCT demonstrates complete metabolic resolution of the primary tumor and nodal metastases. A and E, Maximum intensity projection views. B−D and F−H, Fused PET/CT images.

Fig 8.

Therapy assessment, partial response. A 67-year-old male patient with a history of recurrent SCC of the oral tongue, SCC of the midesophagus, and SCC of the left soft palate (T2N0M0) status postresection with negative margins, who presented with a recurrent left neck mass. The pretherapy PET/CT demonstrates FDG hypermetabolic left level I nodal recurrence (red arrow), and the patient completed chemoradiotherapy to the recurrent tumor in his left neck with IMRT to a dose of 70 Gy. A 12-week posttherapy PET/DCT scan demonstrates residual activity (gold arrow) in the periphery and central necrosis of the left neck nodal mass, representing partial response and a new recurrence of the esophageal malignancy (green arrow).