Soft palate squamous cell carcinoma (SCC) is an uncommon variety of oropharyngeal SCC, a type of cancer which has seen its incidence rise from 1999-2012. These types of cancers are often difficult to detect early; at these later stages, soft palate SCCs have a much worse prognosis (T4 tumors: 36% local-regional control rate). Late stage tumors are frequently associated with metastasis to neck lymph nodes; Stage III or IV are usually associated with at least N1 nodal involvement. Middle drainage to the level II (submandibular) lymph nodes is the most common drainage pattern seen in soft palate SCC. The purpose of this study is to assess the relationship between survival outcomes in soft palate SCC and the involvement of specific groups of neck lymph nodes.
A population-based search for patients diagnosed with squamous cell carcinoma of the soft palate was performed using the case-listing session protocol of the National Cancer Institute’s Surveillance Epidemiology and End Results (SEER) 18 database. 1930 patients with soft palate SCC and documented lymph node information were identified; 1306 had no lymph node involvement, while 624 had metastasis to at least one of the neck lymph nodes. Statistical analysis on overall (OS) and disease-specific (DSS) survival was performed with R software with significance set at p<0.05.
Involvement of LN IV and retropharyngeal LN (RPLN) involvement is associated with the worst OS and DSS. No difference in survival outcomes were observed between patients with between LN IV and RPLN for OS (p = 0.27) or DSS (p = 0.24), so it was not possible to determine which one is associated with the worst survival outcomes. Additionally, for patients with the involvement of only a single lymph node, survival outcomes did not depend on which particular lymph node was involved (p = 0.14). Multivariate Cox Regression shows that the involvement of LN IV and RPLN is associated with worse OS and DSS outcomes (p = 0.02 and p < 0.01, respectively).
The most commonly involved in soft palate SCC are LNs are level II, followed by I, III, V, IV and retropharyngeal (in decreasing order). Involvement of RPLN and LNV are associated with the worst survival outcomes. For future studies, similar lymph node analysis could be performed for SCC of the hard palate or other parts of the oral cavity, and a more generalized model of the effects of lymph node involvement on survival could be obtained.