Delineation of Neck Node Levels for Patients with Locally Advanced Supraglottic Cancer Receiving Radical IMRT: A Cross-Sectional Study in Mainland China

Background: and purpose: In the era of IMRT for locally advanced supraglottic cancer (LA-SGC), the delineation of lymph node clinical target volumes (LN-CTV) remains controversial. We aim to survey the diversity of LN-CTV for LA-SGC patients undergoing radical radiotherapy in mainland China and to provide a basis for improving delineation consistency. Methods: : Radiation oncologists from one provincial cancer hospital, one randomly chosen provincial general hospital and one randomly chosen municipal general hospital from each of the 30 provinces of mainland China participated. The study included four representative cases (T2N1, T3N2b, T4N0, T4N2c) of LA-SGC chosen from the following four different groups: non-T4, low nodal burden (T2-3N0-1); non-T4, high nodal burden (T2-3N2-3); T4, low nodal burden (T4N0-1); and T4, high nodal burden (T4N2-3). Respondents were asked which lymph node levels should be included in high-risk (HR) or low-risk (LR) CTV for nodal prophylactic irradiation. The impact of risk factors was also assessed. Results: : Altogether, 164 chief or attending physicians completed valid questionnaires from all 82 hospitals in China. The criteria that HR-CTV included the node levels with positive lymph nodes and the next lower adjacent level (83.8%–90% agreement) were followed by most physicians (n=160, 97.6%). In the N0-1 stage (cases 1 and 3), ipsilateral levels II and III selected as HR-CTV and level IV as LR-CTV reached good agreement. Whether contralateral levels II and III should be included in HR- or LR-CTV remained controversial; more respondents were inclined to choose them as HR-CTV in case 3 (61.3%). Some respondents supported including contralateral level IVa in LR-CTV (61.9%-68.1%). In the N2 stage (cases 2 and 4), bilateral levels II–IVb other than HR-CTV regions were all included in LR-CTV was indicated in most respondents (75%–92.5%). Levels Ib and V were more likely included in CTV when there were multiple positive lymph nodes in the ipsilateral neck, and more respondents selected level V as HR-CTV in case 4. Nearly half of respondents selected ipsilateral level VIb as CTV when the subglottic region was involved (50.6%, 46.2% and 56.2% in cases 2 to 4, respectively). Tumours crossing the midline (141, 86%), extracapsular spread (132, 80.5%), T stage (142, 86.5%) and N stage (154, 93.9%) as risk factors influencing nodal level selection were shown to have good agreement (≥80%). Conclusion: Most physicians selected involved nodal levels and lower adjacent levels as HR-CTVs in mainland China. Whether bilateral levels II–IV are included in CTV reached relative consensus but poor agreement for HR- or LR-CTV. The selection conditions of levels Ib, Va/b and VIb as CTVs require further research.