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Table of Contents   
REVIEW ARTICLE  
Year : 2012  |  Volume : 23  |  Issue : 6  |  Page : 819-821
Imaging modalities in head-and-neck cancer patients


1 Department of Oral and Maxillofacial Surgery, Vydehi Institute of Dental Sciences and Research Center, Bangalore, India
2 Department of Oral Medicine and Radiology, Vydehi Institute of Dental Sciences and Research Center, Bangalore, India

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Date of Submission06-Feb-2011
Date of Decision27-Jan-2012
Date of Acceptance15-Apr-2012
Date of Web Publication3-May-2013
 

   Abstract 

Accurate staging and timely assessment is critical in head-and-neck cancer patients for formulating the appropriate treatment strategy. Therefore, optimizing pretreatment imaging for diagnosis is of great importance. Computerized tomography (CT), introduced in the early 70s, followed by magnetic resonance imaging (MRI) and positron emission tomography (PET), refinements in ultrasonography (USG), advances in nuclear medicine, and applications such as sentinel node lymphoscintigraphy have greatly added to diagnostic accuracy. Post-treatment CT or MRI is of value when a recurrent tumor is suspected. It can confirm the presence of such a lesion and determine its extent. This is important information for determining the possibility of salvage therapy.

Keywords: Computed tomography, magnetic resonance imaging, multidetector row CT, positron emission tomography, sentinel lymph node scintigraphy

How to cite this article:
Sham M E, Nishat S. Imaging modalities in head-and-neck cancer patients. Indian J Dent Res 2012;23:819-21

How to cite this URL:
Sham M E, Nishat S. Imaging modalities in head-and-neck cancer patients. Indian J Dent Res [serial online] 2012 [cited 2020 Nov 28];23:819-21. Available from: https://www.ijdr.in/text.asp?2012/23/6/819/111270
The last 30 years have seen an explosion of technical advances in the diagnosis of oral cancer. Accurate staging of patients with head-and-neck squamous cell carcinoma (HNSCC) is critical for treatment selection, as treatment decisions are influenced by delineation of the primary tumor, the presence and extent of lymph node metastases, and presence of distant metastases.

Computerized tomography (CT), introduced in the early 70s, followed by magnetic resonance imaging (MRI) and positron emission tomography (PET), refinements in ultrasonography (USG), advances in nuclear medicine, and applications such as sentinel node lymphoscintigraphy have greatly added to diagnostic accuracy. It is important to determine the right indications for these new diagnostic techniques.


   Primary Tumor Top


The most important information required for proper therapeutic planning is accurate knowledge regarding location, size, extent, and depth of invasion of a primary tumor and its relation to the surrounding structures. [1] The sensitivity of FDG-PET (F-18-fluorodeoxyglucose-positron emission tomography) is reported to be 98% and that of FDG-PET-CT 97% for the detection of primary tumors in patients with newly diagnosed HNSCC. PET alone cannot delineate the extent of the tumor. [2] Since physical examination usually reveals the primary tumor, the role of FDG-PET is limited to the detection of occult primary tumors in patients with cervical lymph node metastases in the neck. [1]


   Lymph Node Metastases Top


Since the status of the cervical lymph nodes is the single most important tumor-related prognostic factor, optimal treatment planning requires knowledge of the exact extent of involvement of the neck nodes. It is obvious that patients who clinically manifest lymph node metastases require some form of treatment. A meta-analysis showed that for the detection of lymph node metastases, conventional imaging techniques like CT, MRI, USG and, especially, USG-guided fine-needle aspiration cytology are more reliable than palpation. [3]

It was also found in a meta-analysis that FDG-PET has good performance in the overall pretreatment evaluation of the presence of lymph node metastases in HNSCC patients. [4] Detection of occult lymph node metastases is the most important problem. The meta-analysis showed that FDG-PET detects only 50% of the occult lymph node metastases, reiterating the inability of imaging test to document microscopic disease. [4] One study showed that for the detection of subclinical lymph node metastases the visual correlation of FDG-PET with CT/MRI was more accurate than FDG-PEt alone. [5] Although PET and PET- CT have probably the best accuracy for detecting occult cervical lymph node metastases in the clinically N0 neck, these techniques are still not reliable enough to help the clinician to avoid elective treatment of the neck. [1]

In patients without clinical signs of lymph node involvement, the sensitivity of FDG-PET is only 50%. This has led to the use of sentinel lymph node scintigraphy, which seems to be a valid alternative to elective stage dissection. The sentinel lymph node (sN) concept is fundamentally based on the theory of the orderly spread of tumor cells within the lymphatic system. The first lymph node in a regional lymphatic basin that receives lymphatic flow from a tumor is considered to be the sN. In the sN procedure this lymph node is identified using radioactive colloid and blue dye. The sN is examined in detail by histopathologically, using stepped serial sectioning and immunohistochemistry. The sN concept assumes that lymphatic metastases are always identified in the sN, so that a tumor-negative sN precludes the presence of lymphatic malignant involvement. The sensitivity of this technique was estimated as 93%. [6] The sN procedure is less reliable if the (sentinel) lymph node contains a large tumor deposit. [7] Therefore, other imaging techniques, such as USG-guided fine-needle aspiration cytology (FNAC), are needed to select patients for the sN procedure to avoid false negative findings.

New high-resolution MRI sequences and the development of specific contrast agents are offering new possibilities in the diagnostic workup of head-and-neck lymph nodes. Diffusion-weighted (DW) MRI uses the apparent diffusion coefficient (ADC) as a marker of cell density. The ADC is highest in benign lymphadenopathy and lowest in metastatic nodes. However, the presence of necrosis in metastatic cancers increases the ADC of the nodes. Therefore, DW MRI is considered complementary to standard MRI. Greater use of DW MRI in routine clinical practice probably will depend on improvements in the standardization of the imaging technique and its interpretation. [1]


   Detection of Distant Metastases Top


The reported incidence of clinically identified distant metastases in HNSCC at presentation varies from 2%-18%. [8] This incidence is directly related to the stage of disease, particularly to the presence and extension of lymph node metastases and locoregional control, and depends on the applied diagnostic methods. [8] FDG-PET is a sensitive whole-body technique that has shown potential for use in the detection of distant metastases. [9] Most studies that have used FDG-PET in screening for distant metastases have lacked fair and controlled comparison between PET and other standard conventional imaging (such as chest CT) and/or an adequate gold standard (such as reasonable follow-up). [10] FDG-PET had relatively high sensitivity and high predictive positive value. One concern of using FDG-PET for screening is its cost. On one hand, FDG-PET is an expensive diagnostic technique and, on the other hand, detection of distant metastases will allow avoidance of futile expensive treatment.

FDG-PET lacks precise anatomical resolution and may overdiagnose some inflammatory conditions. By virtue of its high spatial resolution, multidetector row CT (MDCT) may serve as a cross-sectional imaging tool that can complement FDG-PET in the evaluation of distant metastases in HNSCC patients and may help to characterize FDG abnormalities. [1] The combination of PET and CT in PET-CT is an attractive option, potentially combining the best of both worlds and providing a one-stop shop for the patient. In recent years, dual-modality PET-CT has been used to provide accurately fused functional PET and morphological CT in a single examination. [1]

In clinical practice, the detection of asymptomatic distant metastases during follow-up is of relatively little importance since currently no curative treatment options are available. Unfortunately, comparisons between the accuracy of CT, PET, visual correlation of PET and CT, and integrated PET-CT were not made. Due to the introduction of multi-receiver channel MR, whole-body MRI (WB-MRI) has become clinically feasible, with substantially reduced examination times. WB-MRI shows promise for detecting metastases of primary head-and-neck tumors. [11]


   Imaging During (Chemo) Radiotherapy Top


Measurable anatomic changes occur during the course of radiotherapy for head-and-neck cancers, mainly during the second half of the treatment. Such volumetric and geometric changes can have a potential dosimetric impact when conformal treatment techniques are applied. Compared to pretreatment CT, the per-treatment tumor volume appeared significantly smaller on MRI than on CT. Per-treatment automatic segmentation of tumor volume on FDG-PET is not possible due to tremendous increase in background signal due to radiation-induced inflammation. [12]


   Post-Treatment Imaging Top


After treatment of a head-and-neck cancer, a number of tissue changes become visible on CT and MR images of the neck. These expected alterations should be known, so that they are not misinterpreted as evidence of persistent or recurrent tumor. In patients with a high risk profile for tumor recurrence after treatment, imaging is of value for surveillance of the patient and can be used as an adjunct to clinical follow-up. Imaging may be used to monitor tumor response and to detect recurrent or persistent disease before it becomes clinically evident, possibly providing a better chance for successful salvage. Some authors recommend FDG-PET for detecting residual nodal disease. However, FDG-PET obtained early after the end of therapy appears to be unreliable. [13]


   Conclusion Top


Sophisticated imaging methods play an increasingly important role in the management of head-and-neck cancer. Pretreatment imaging findings have predictive value for patient outcome, independent of the currently used TNM classification, and can be used to tailor treatment plans. Based on per-treatment imaging, individualized replanning during radiotherapy may ameliorate tumor control rates and reduce toxic effects on normal tissues.

Post-treatment CT or MR imaging is of value when a recurrent tumor is suspected and can confirm the presence of such a lesion and determine its extent. More rarely, imaging may be useful for differentiating between tumor recurrence and treatment complications.

 
   References Top

1.de Bree R, Castelijns JA, Hoekstra OS, Leemans CR. Advances in imaging in the work-up of head and neck cancer patients. Oral Oncol 2009;45:930-5.  Back to cited text no. 1
    
2.Roh JL, Yeo NK, Kim JS, Lee JH, Cho JJ, Choi SH, et al. Utility of 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography and positron emission tomography/computed tomography imaging in the preoperative staging of head and neck squamous cell carcinoma. Oral Oncol 2007;43:887-93.  Back to cited text no. 2
    
3.de Bondt RBJ, Nelemans PJ, Hofman PAM, Casselman JW, Kremer B, Engelshoven, et al. Detection of lymph node metastases in head and neck cancer: A meta-analysis comparing US, USgFNAC, CT, and MR imaging. Eur J Radiol 2007;64:266-72.  Back to cited text no. 3
    
4.Kyrzas PA, Evangolou E, Denaxa Kyza D, Ionnidas JPA. 18F-Fluorodeoxyglucose positron emission tomography to evaluate cervical node metastases in patients with head and neck squamous cell carcinoma: A meta-analysis. J Natl Cancer Inst 2008;100:712-20.  Back to cited text no. 4
    
5.Ng SH, Yen TC, Chang JTC, Chan SC, Ko SF, Wang HM, et al. Prospect study of [18F]Fluorodeoxyglucose positron emission tomography and magnetic resonance imaging in oral cavity squamous cell carcinoma with palpably negative neck. J ClinOncol 2006;27:4321-6.  Back to cited text no. 5
    
6.Ross GL, Soutar DS, MacDonald DG, Shoib T, Camilleri I, Roertson AG, et al. Sentinel node biopsy in head and neck cancer: Preliminary results of a multicenter trial. Ann SurgOncol 2004;11:690-6.  Back to cited text no. 6
    
7.Steokli SJ, Pfaltz M, Ross G, Steinert HC, MacDonald DG, Wittekind C, et al. The second international conference on sentinel node biopsy in head and neck cancer. Ann Surg Oncol 2005;12:919-24.  Back to cited text no. 7
    
8.de Bree R, Deurloo EE, Snow GB, Leemans CR. Screening for distant metastases in patients with head and neck cancer. Laryngoscope 2000;110:397-400.  Back to cited text no. 8
    
9.Brouwer J, Senft A, de Bree R, Comans EFI, Golding RP, Castelijens JA, et al. Screening for distant metastases in patients with head and neck cancer: Is there a role for 18 FDG-PET? Oral Oncol 2006;60:58-66.  Back to cited text no. 9
    
10.Senft A, de Bree R, Hoekstra OS, Kuik DJ, Golding RP, Oyen WJG, et al. Screening for distant metastases in head and neck cancer patients by chest CT or whole body FDG-PET: A prospective multicenter trial study. Radiother Oncol 2008;87:221-9.  Back to cited text no. 10
    
11.Ng SH, Chan SC, Liao CT, Chang JT, Ko SF, Wang HM, et al. Distant metastases and synchronous second primary tumors in patients with newly diagnosed oropharyngealanahypopharyngealcarcinomas:evaluation of (18)F-FDG PET and extended-field multi-detector row CT. Neuroradiology 2008;50:969-79.  Back to cited text no. 11
    
12.Hermans R. Head and neck cancer: How imaging predicts treatment outcome. Cancer Imaging 2006;6(Spec No A):S145-53.  Back to cited text no. 12
    
13.Hermans R. Post-treatment imaging of head and neck cancer. Cancer Imaging 2004;4(Spec No A):S6-15.  Back to cited text no. 13
    

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Correspondence Address:
M E Sham
Department of Oral and Maxillofacial Surgery, Vydehi Institute of Dental Sciences and Research Center, Bangalore
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.111270

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    Abstract
   Primary Tumor
    Lymph Node Metas...
    Detection of Dis...
    Imaging During (...
    Post-Treatment I...
   Conclusion
    References

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