Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_27_2642 - Lymph node ratio as a predictor of distant metastases in major salivary gland carcinomas

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Lymph node ratio as a predictor of distant metastases in major salivary gland carcinomas
N. T. A. Nguyen1, S. H. Huang2, W. Xu3, Y. Zhang3, A. J. Bayley2, S. V. Bratman2, J. Cho2, M. E. Giuliani2, A. J. Hope2, J. Kim2, B. O'Sullivan2, J. G. Ringash4, J. N. Waldron2, A. Hansen5, J. de Almeida6, E. Monteiro7, D. B. Chepeha8, J. Irish8, D. Goldstein8, and A. Hosni1; 1Department of Radiation Oncology, Princess Margaret Cancer Centre- University of Toronto, Toronto, ON, Canada, 2Department of Radiation Oncology, Princess Margaret Cancer Centre-University of Toronto, Toronto, ON, Canada, 3University of Toronto, Toronto, ON, Canada, 4Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada, 5Department of Medical Oncology, Princess Margaret Cancer Centre-University of Toronto, Toronto, ON, Canada, 6Department of Otolaryngology - Head & Neck Surgery, University Health Network- University of Toronto, Toronto, ON, Canada, 7Department of Otolaryngology - Head & Neck Surgery, Mount Sinai Hospital-University of Toronto, Toronto, ON, Canada, 8Department of Otolaryngology - Head & Neck Surgery, University Health Network-University of Toronto, Toronto, ON, Canada

Purpose/Objective(s): To investigate the prognostic value of lymph node ratio (LNR, number of positive lymph nodes[LN]/total number of excised LN) on distant metastases (DM) and overall survival (OS) in patients (pts) with major salivary gland carcinoma (SGC).

Materials/Methods: An REB-approved retrospective review was conducted for SGC patients treated at our institution with curative surgery and neck dissection (>=6 dissected LN)+/-adjuvant treatment in 2000-2015. Patients, treatment and outcomes data were collected from our institutional maintained databases. Staging was reviewed according to the AJCC-UICC 8th edition. High risk pathology was defined with histologic grade and WHO histologic criteria, and included: adenoid cystic carcinoma (ACC), salivary duct carcinoma, SCC, G2/3 adenocarcinoma, G2/3 mucoepidermoid carcinoma (MEC), G2/3 carcinoma ex-pleomorphic adenoma, carcinosarcoma, undifferentiated (small-, large-cell or lymphoepithelial) carcinoma and G3 of other histologic subtypes. Distant control (DC) and OS were analyzed with competing risk and Kaplan-Meier methods respectively. LNR (continuous variable) was subjected to multivariable analysis (MVA) for DM and OS (adjusted for age, gender, primary SGC subsite, pathologic stage, high-risk pathology, lymphovascuar invasion [LVI], perineural invasion [PNI], extranodal extension [ENE] and surgical margin status). The optimal cutpoint of LNR that maximized the difference in outcomes was determined using maximally selected rank statistics. Subgroup analysis was performed for patients with pN+.

Results: A total of 204 pts were identified: median age: 56 yr (16-91); median follow-up: 5.2 yr (0.4- 17.6); parotid gland primary tumor location: 168 (82%); high risk pathology: 151 (74%); pT3-4: 132 (65%), pN+: 99 (44%); LVI: 49 (26%); positive microscopic surgical margin: 103 (52%); ENE: 37 (19%). PORT was used in 195 pts (96%); and adjuvant concurrent chemotherapy in 11 (5%). Of 2,725 LNs evaluated, 328 (12%) were pN+. The median number of dissected LN was 23 (6–101). For pN+ pts, the median number of involved LN was 3 (1-65) and median LNR was 14% (1%–100%). High-risk pathology and LVI were associated with high LNR (p<0.001 for both). On MVA LNR was independently correlated with DM (HR:1.18, 95%CI: 1.07-1.30, p<0.001) and OS (HR:1.16; 95%CI: 1.06-1.28, p=0.002) and so did LVI+ (DM: HR:2.54, 95%CI: 1.38-4.70, p=0.003) and OS (HR:2.50; 95%CI: 1.33-4.70, p=0.004), positive margins (DM: HR:2.47, 95%CI: 1.31-4.65, p=0.005) and OS (HR:2.59; 95%CI: 1.35-4.95, p=0.004),. The optimal cut-off point for LNR was 8%; 5-yr DC: 42% vs 88%, p<0.001; 5-yr OS: 44% vs 89%, p<0.001 for LNR ≥8% vs <8%. In a subgroup analysis of patients with pN+, LNR remained predictive for DM (HR:1.24, 95%CI: 1.14-1.35, p<0.001) and OS (HR 1.27, 95%CI: 1.16-1.38, p<0.001).

Conclusion: High LNR is associated with a higher risk of DM and lower OS. LNR should be evaluated in future prospective studies for intensified therapy or surveillance schedule in patients with SGC.

Author Disclosure: N.A. Nguyen: None. S. Huang: None. W. Xu: None. S.V. Bratman: None. J. Cho: None. M.E. Giuliani: Honoraria; Elekta Inc. Travel Expenses; Elekta Inc. Chair, Education Committee; Canadian Association of Radiation Oncology. A.J. Hope: Travel Expenses; Elekta, Inc. B. O'Sullivan: Partner; University of Toronto. Chair, Prognostic Factors Task Force, TNM Committe; Union for International Cancer Control (UICC). A. Hansen: None. J. de Almeida: None.

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