Do neck levels negative on initial CT need to be dissected after definitive radiation therapy with or without chemotherapy?

Background: The extent of the adjuvant neck dissection after radiotherapy with or without chemotherapy remains undefined. We investigated whether we could limit neck dissection to levels with positive lymph nodes on CT scan before treatment.
Methods: Twenty-one patients' initial diagnostic CT scans were reviewed retrospectively and neck levels were scored positive for malignancy if the respective lymph nodes met any of the following: maximum axial diameter >1 cm; oval/round shape; hypodensity; presence of extracapsular penetration; and irregular enhancement. Patients were treated with radiation alone (71%) or with radiation plus chemotherapy (29%). Neck dissection consisted of radical (8 heminecks), modified radical (4 heminecks), or selective (13 heminecks).
Results: One hundred two neck levels were dissected. Of these, 56 levels (54.9%) were negative on initial CT scan. None of them was found to contain cancer.
Conclusions: After radiation with or without chemotherapy, neck dissection of an initially negative neck level may not be necessary. Neck dissection may target only initially positive levels.