Detection of Residual Disease of Lymph Node Metastases in the Neck, Which Is Treated by (Chemo)radiation

In this issue of the AJNR, Ojiri et al report on size changes as seen on pre-radiation therapy and post-radiation therapy CT scans of lymph nodes of patients with regional metastases from head and neck squamous cell carcinoma as a predictor of pathologic outcome after surgical treatment of the neck. Regional metastasis is the most important factor in the prognosis of patients with head and neck squamous cell cancer. Generally, treatment of head and neck squamous cell cancer is based on the stage of the disease at the time of presentation (1). Stage I and II disease is effectively treated with either surgical excision or radiation therapy, whereas stage III and IV disease, characterized by larger locally invasive tumor or lymph node metastases or both, is generally treated with combined surgery and radiation therapy.

More recently, chemoradiation has also proved to be effective in the treatment of advanced disease, especially in preserving vital organs while maintaining cure rates similar to those associated with a combination of surgery and radiation therapy (2). This treatment, however, remains experimental, and the jury is still out regarding whether this is a preferable treatment plan. Nonetheless, through the expanding role of (chemo)radiation therapy for organ preservation and unresectable head and neck squamous cell cancer, the dilemma of whether surgical therapy is indicated to treat gross nodal disease has surfaced. It is logical that efforts currently are focusing on prognostic factors to determine which patients would benefit from neck dissection and which patients could be spared such additional morbidity (3).

Post-treatment radiographic studies, such as those proposed by Ojiri et al, comprise a noninvasive means of monitoring the response to therapy. Ojiri et al find that heminecks, in which the percentage decrease ratio of the largest node was >50% from pre-radiation therapy to post-radiation therapy CT scans, tended to have a negative surgical specimen if the neck was routinely dissected as their protocol prescribed. However, this trend was not statistically significant. The first statement in their conclusion is therefore not surprising, but the second statement that there still is a relation, albeit weak, deserves more attention. In a recently published article, the same authors found other factors, such as the size of the nodes and the presence of intranodal low attenuation and extranodal growth on post-treatment CT scans, to be predictors of the pathologic result of a planned post-radiation therapy neck dissection (4). A combination of these predictors or even other criteria may well increase the accuracy of CT to detect residual metastatic spread in lymph nodes. It is therefore not understandable why the authors did not perform this same analysis on their post-radiation therapy scans in the present study. Moreover, in addition to analyzing lymph node response, the use of volume estimation may provide a more accurate determination of lymph node size and may well provide a high accuracy of prediction. This is in contrast to area estimations, for which measurements are made only in the axial plane and which may result in an inaccurate nodal size assessment.

The use of CT to follow clinical response offers certain advantages, such as low cost and ease of availability, over techniques such as fluorine-18-fluorodeoxyglucose positron emission tomography, which is currently under investigation for this indication at various institutions. The potential of ultrasonography-guided fine needle aspiration cytology, which also has low cost and ease of availability, should be mentioned in this respect. A wait-and-see policy for the clinical N0 neck with strict follow-up with ultrasonography-guided fine needle aspiration cytology already proved to be justified in patients with early staged oral or oropharyngeal squamous cell carcinoma who underwent transoral tumor excision (5). A wait-and-see policy after negative results of ultrasonography-guided fine needle aspiration cytology and strict follow-up with ultrasonography-guided fine needle aspiration cytology has not been applied to a large group of patients with positive necks that have been irradiated. This clinical approach to the patient with nodal disease may also be worthwhile to explore in a larger study population as part of an organ preservation protocol.

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