Current oncologic concepts and emerging techniques for imaging of head and neck squamous cell cancer

Abstract

The incidence of head and neck squamous cell carcinoma (HNSCC) is increasing and currently they account for 5% of all malignancies worldwide. Inspite of ongoing developments in diagnostic imaging and new therapeutic options, HNSCC still represents a multidisciplinary challenge.One of the most important prognostic factors in HNSCC is the presence of lymph node metastases. Patients with confirmed nodal involvement have a considerable reduction of their 5-year overall survival rate. In the era of individually optimised surgery, chemotherapy and intensity modulated radiotherapy, the main role of pre- and posttherapeutic imaging remains cancer detection at an early stage and accurate follow-up. The combined effort of early diagnosis and close patient monitoring after surgery and/or radio-chemotherapy influences disease progression and outcome predicition in patients with HNSCC.This review article focuses on currrent oncologic concepts and emerging tools in imaging of head and neck squamous cell cancer. Besides the diagnostic spectrum of the individual imaging modalities, their limitations are also discussed. One main part of this article is dedicated to PET-CT which combines functional and morphological imaging. Furthermore latest developments in MRI are presented with regard to lymph node staging and response prediction. Last but not least, a clinical contribution in this review explains, which information the head and neck surgeon requires from the multimodality imaging and its impact on operation planning.

Keywords: HNSCC; MRI; PET-CT; diffusion weighted imaging; head and neck carcinoma; hypoxia imaging; lymph node staging.

Table 1. Sensitivity and specificity of CT, MRI and PET-CT for detection of cervical lymph node metastases

Table 2. Value of 18F-FDG PET-CT for response evaluation and outcome prediction in patients with HNSCC

Table 3. Overview of current literature for DWI MRI in HNSCC

Table 4. Relationship between original DW images and corresponding ADC-value

Table 5. Prediction of therapeutic response

Figure 1. 43-year-old male with T4N2cM1 right sided supraglottic laryngeal cancer (Fig. 1a on the left, black star) and ipsilateral lymph node metastases in the right cervical level III (Fig. 1a on the left, white arrow).

The pulmonary window setting in the axial CT MIP demonstrates at least 4 metastases in segment 6 of both pulmonary lobes (Fig. 1b on the right side, black stars).

Figure 2. 77-year-old male with T3N2M1 cancer of the floor of the mouth on the right side. The soft tissue window setting in post contrast CT demonstrates an extensive hyperdense tumor with osteodestruction of the mandible (Fig. 2a, black star). Additionally a histologically confirmed lymph node metastases with central necrosis in the right sided cervical level II is visible (Fig. 2a, white arrow).

The bone window setting shows the osteodestruction of the mandible (Fig. 2b, black star). 72-year-old male with T3N3 oropharyngeal cancer. Extensive bilateral neck lymph node metastases with encasement of the carotid artery on both sides (Fig. 2c, white arrow). Coronary CT image reconstruction demonstrates a both sided tumor infiltration of the carotid bifurcation (Fig. 2d, white arrow).

Figure 3. 51-year-old male with diagnosis of a T3N2M0 cancer of the base of the tongue on the left side. Post contrast CT shows a necrotic lymph node metastasis 3 cm in size in the left cervical level II (Fig. 3a, black star). On coronal CT slices lymph node metastases in the left level II and III are visible (Fig. 3b, black star; Fig. 3d and 3f). PET demonstrates intensive FDG uptake by the lymph node metastases (Figure 3e and 3f). A lymph node of 1.5 cm in the right neck level II could not be assessed with CT (Fig. 3a and 3b, white arrow). This lymph node shows intensive FDG Uptake in PET (Fig. 3e and 3f) and the fused axial and coronary PET-CT images (Fig. 3c and 3d). Bicervical neck dissection was performed. Histologically a lymph node metastasis was confirmed.

Intensive contrast agent accumulation in the primary tumor in the left sided base of the tongue (Fig. 3a, 2 white arrows) which correlates with intensive FDG uptake in PET-CT (Fig. 3c and 3e).

Figure 4. 53-year-old male with right sided cancer of the tonsil and histologically proven lymph node metastasis in the right neck level II (big lymph node) and two smaller lymph node metastases in level III (black circle). Standard reconstructions of the PET data with 3 iterations, 24 subsets, Gaussian filter 3 mm FWHM (Fig. 4a on the left side) and TOF reconstruction 3 mm with 3 iterations and 21 subsets (Fig. 4b on the right side). The 2 small lymph node metastases in the right neck level III appear with more sharply bounded outline and less blurring in the TOF reconstruction.

Figure 5. Lymph node metastasis in a patient with left-sided HNSCC of the oropharynx shows substantial diffusion restriction with signal increase in the axial original DW image (b) and corresponding decrease of the ADC value (a). Correlating display of the LN in the coronal fat-suppressed, fluid-sensitive STIR (c) and T1-weighted fat-suppressed image after contrast media (d).