Patterns of local extension and nodal involvement in early stage nasal NK/T-cell lymphoma and delineation of clinical target volume

Abstract

Objective To define the patterns of local extension and nodal involvement in patients with early stage nasal NK/T-cell lymphoma, and to improve the delineation of clinical target volume.Methods Two hundred and twenty-two patients consecutively diagnosed with nasal NK/T-cell lymphoma were reviewed.All patients had stage Ⅰ E/Ⅱ E diseases.CT/MRI images were reviewed to determine the local invasion of adjacent organs or structures and involvement of lymph node.Results 143 of 222(64%) patients had primary tumor extended into adjacent organs or structures from nasal cavity.According to the incidence rates of tumor extension, the involved organs or structures were subclassified into three subgroups:high risk (≥40%):ethmoid sinus (60%) and maxillary sinus (55%);intermediate risk (5%-40%):nasopharynx (39%), skin (22%), oropharynx (12%), orbit (10%), and hard palate (10%);and low risk (≤5%):sphenoid sinus (3%), soft plate (3%),frontal sinus (3%) and skull base (1%).Cervical lymph node metastasis occurred in 16%(36/222) of the patients and these patients were staged as Ⅱ E.Thirty-three patients with stage Ⅱ E disease had available images and were analyzed for the pattern of nodal involvement.Submandibular or submental (57%) and the upper cervical lymph nodes (57%) were the most commonly involved sites of nodal region.For the 24 patients with primary tumor located in the unilateral nasal cavity, 54% presented with contralateral cervical lymph node metastasis.Whereas for the 9 patients with primary tumor located in the bilateral nasal cavity, 57% had bilateral cervical lymph node metastasis.For the 88 patients with extensive stage Ⅰ E disease who did not receive irradiation to the cervical lymph node, only one patient (1%) had disease relapse in cervical lymph node.Furthermore, all patients with disease extended to nasopharynx (n= 23) or oropharynx (n= 8) did not receive prophylactic cervical lymph node irradiation, and none of them developed cervical lymph node relapse.Conclusions The delineation of clinical target volume for early stage nasal NK/T-cell lymphoma should be determined by the risk of involvement of paranasal structures and cervical lymph node.Prophylactic neck irradiation is not recommended for patients with stage Ⅰ disease. Key words: NK/T-cell Lymphoma, nasal cavity/intensity-modulated radiotherapy; Local extension patterns; Clinical target volume delineation