1. H. AlHussain, I. Busca, L. Eapen,, S. El-Sayed The Ottawa Hospital Cancer Center, University of Ottawa Department of Radiation Oncology

2. No Disclosures

3. Purpose To evaluate whether involvement of various Nodal Levels are associated with a different risk of Distant Metastasis (DM) in Patients with Head and Neck Squamous Cell Carcinoma (HNSCC).

4. Methods - A prospective study have accrued 92 HNSCC patients (Stage II-IVa). - Treated using Intensity Modulated Radiation Therapy on a Helical Tomotherapy unit. - Total dose of 70 Gy +/- Concurrent Platinum Based Chemotherapy. - 88 patients included in this report have completed the treatment as per the protocol. - The majority of patients were males (69 patients) with a median age of 60 years (39-87). - Primary involved sites were Oropharynx (59 patients), Larynx (10), Nasopharynx (7), Hypopharynx (6), Oral Cavity (3) and Unknown Primary (3). - Lymph Nodal (LN) levels were identified using their diagnostic/planning CT scans, MRI or FDG-PET scans based on size/morphology/contrast enhancement or FDG avidity. - Different LN levels were defined based on the Consensus Guidelines (V.Gregoire, et al). - For each LN level, the percentage crude risk of DM was identified by calculating “No. o f patients with the involved LN Level who developed DM” / “the total number of patients who had that LN level involved”.

6. Results - The patients were followed-up for a median period of 31 months (3-65). - Thirteen patients (15%) developed Distant Metastasis with a median time to DM of 20 months (1-44 months). - Level I (9 pts), Level II (61 pts), Level III (40 pts), Level IV (18 pts), Level V (13 pts) and RP (6 pts). - Out of the 13 patients who developed DM, the LN levels involved were: Level I (3 pts), Level II (12 pts), Level III (8 pts), Level IV (7 pts), Level V (6 pts) and RP group (2 pts). - The crude risk of DM stratified based on each LN level was calculated as follows: Level I (33%), Level II (20%), Level III (20%), Level IV (39%), Level V (46%) and RP group (33%). - The 3 patients with DM who had Level I LN involved had extra-oral cavity primaries with multi-level involvement (Supraglottic Larynx “level I-V”, Base of Tongue ”Levels I,III,IV” and Tonsil “Level I-II”). - The most common site for DM was lung (8 pts), followed by bones (5 pts), liver (2 pts) and brain (1 pt).

7. Conclusions Patients with HNSCC who have involved Lymph Node levels IV, V or RP group are associated with 33-46 % risk of DM in this cohort and should be considered to be further assessed for the role of adjuvant systemic therapy.