Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_40_2538 - The Impact of Subclinical Regional Metastases on the Outcomes of Patients With Head and Neck Adenoid Cystic Carcinoma

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

The Impact of Subclinical Regional Metastases on the Outcomes of Patients With Head and Neck Adenoid Cystic Carcinoma
B. W. Beard, O. Bhattasali, N. Cnossen, J. Chen, and S. Iganej; Southern California Permanente Medical Group, Los Angeles, CA

Purpose/Objective(s): The impact of occult lymph node metastases in adenoid cystic carcinoma of the head and neck (HNACC) is unknown. We sought to determine the incidence, predictors, and outcomes of occult lymph node metastases in HNACC. We hypothesized that the presence of occult lymph node metastases would be associated with poorer overall survival, locoregional control, and distant metastasis free-survival (DMFS).

Materials/Methods: We identified 36 patients treated with elective neck dissection (END) for HNACC at our institution from May 2000 to August 2016 and gathered staging, treatment, histologic, and outcome information in each case. There were 12 (33.3%) male and 24 (66.6%) female patients. Median age at diagnosis was 56.5 years. A majority (61%) of patients had major salivary gland tumors. The most common sites were parotid (n = 14), submandibular gland (n = 6), and oral cavity (n = 5). There were 4 (11.1%) T1, 6 (16.67%) T2, 7 (19.44%) T3, and 17 (47.22%) T4 tumors. All patients were clinically N0 at the time of surgery. We compared patients who were pathologic N+ (pN+) to patients who were pathologic N0 (pN0) after END.

Results: There were 8 (22.2%) patients with occult lymph node metastases; 2 patients had lymph node metastases limited to intraparotid nodes. Thus, the rate of occult cervical lymph node metastases was 16.66%. The number of lymph nodes sampled did not differ significantly between pN+ and pN0 groups (median nodes: pN+ 27 and pN0 24). Although the incidence of lymph node positivity increased numerically with higher T stage, this trend did not achieve statistical significance (T1 – 0%, T2 – 16%, T3 – 28.5%, T4 – 29.4%). Patients with positive nodes were more likely to have lymphovascular invasion identified on surgical pathology (p = 0.04). The majority of patients in each group (75%) received adjuvant radiation. All patients with positive nodes for whom full records were available received regional irradiation, whereas only 1 of 11 pN0 patients received nodal irradiation. Median follow-up from treatment completion for survivors was 4.33 years. There were 3 locoregional recurrences in pN0 patients (2 local failures and one regional failure) and no locoregional recurrences in pN+ patients. Five-year overall survival was 74.15% for pN0 and 52.5% for pN+ patients (p = 0.27). Five-year DMFS was 66.3% in pN0 versus 17.5% in node-positive patients (p = 0.038, HR 0.3).

Conclusion: When the majority of patients with HNACC receive post-operative radiotherapy, subclinical nodal involvement discovered through END does not appear to predict for an increased risk of locoregional failure. In this setting, combined modality therapy results in high rates of locoregional control. Occult nodal involvement correlated with the presence of lymphovascular invasion and was a predictor of worse DMFS. Investigations towards improvement of systemic control are warranted in this population.

Author Disclosure: B.W. Beard: None. O. Bhattasali: None. J. Chen: None. S. Iganej: None.

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